TABLE 1:

THEMES (across items)

Theme	Subtheme	Definition/Explanation	Example Quotes
Unclear and Confusing Terms/Words	Unclear Vocabulary	Use of “hole” in explaining type of sex was not well understood; options for current practices people may use as prevention (eg., “withdrawal” before ejaculation) caused confusion.	P: “On the hole part. […] My issues was that I had a confusion as to what a front and back hole are. […] They are referring to the female. I got confused as to what a back hole was.” -Female participant, 23, Vulindlela P: “No, the only withdrawal I know is the one for withdrawing money.” -Female participant, 20, Cape Town P: Withdrawal means, “let’s just drop it and not have sex”. I: So it is the same as abstinence? P: Yes -Male participant, 21, Vulindlela
	Divergent Interpretation	Abstinence was interpreted by some as a sporadic, non-permanent behavior and by others as long term celibacy. Interpretation of “partner” differed among participants. Some perceived partner to only refer to a romantic relationship, while others interpreted partner as someone who engages in sexual activity with them. Participants expressed varied interpretations of “sexual debut,” including or excluding forced sex and rape, and for MSM whether or not to report first time of heterosexual activity or first sex with another man.	P: “[I use] Abstinence somewhat, because I didn’t have exchange with this guy I think it was last week we didn’t have sex.” -Male participant, 24, Vulindlela P: It [abstinence] is when you refrain from having sex. It is refraining from sex or behaving yourself. I: You don’t have sex at all? P: Yes, you don’t have sex at all. -Male participant, 20, Vulindlela P: Those that have been raped? How would I change it and put it…? But it does need changing cos there are those people who have been raped, maybe a person has been raped at 12 years maybe, I won’t say I started having sex at 12, yes. I’ll speak about the age that I enjoyed it. - Female participant, 19, Vulindlela
	Long Questions are Confusing	Questions that were long, had long lead-in explanations or multiple clarifiers in brackets were more difficult to understand.	P: “It’s like a book the paragraph is too much. Just write anal sex is penis to anus and vaginal sex penis to vagina that’s it.” - Male participant, 24, Vulindlela
Language mismatched (with local language, words used commonly in one’s community)	“Untranslatable” for certain sexual terms	Participants (females) expressed there not being a word for anal sex in isiZulu.	P: “I would change it by saying “all in all how many times do you think you got involved in sexual intercourse performing anal sex”, it is just that I do not know what I am going to say in IsiZulu when it comes to anal sex” I: “Hmm. The problem is there is no term for Anal sex that you know.” P: “Yes for IsiZulu.” -Female participant, 24, Vulindlela
	Words fail to reflect common terms in MSM community	Male participants expressed that there are specific terms that the gay community uses to refer to sexual practices that are different than standard vocabulary	P: And it says where the penis is put inside the anus, meaning it’s talking about the person who inserts and then it says vaginal sex where the penis is put inside, which means it’s talking about the tops, not us bottoms. I: So how would you, what do you think this question is asking? P: Like it’s asking if you have ever had sex, I have never had sex I am a receiver, I never insert my thing on someone, that’s why I say this thing is talking to the giver. I: So in your understand, this question is only for top people? P: Yes. -Male participant, 20, Vulindlela
Self-tailored items	Combining terms to allow MSM and women to answer the same question by selecting the term that applied to them was disliked	Some MSM felt questions were only relevant to tops, not bottoms, and vice versa. MSM who read a question that didn’t apply to them often expressed confusion as to why the researcher would ask the question.	P: Was it important for them to say anal sex? Well…for someone who reads this they’ll just know you are talking about gay guys, because it’s just stated as anal sex, and that’s only gays who do anal sex, ok not only gays but the way it’s asked, it’s straightforward, because look it says anal sex where the penis is put inside the vagina…yes, it’s not relevant in gays. I just feel like it shouldn’t even say anal sex, it should just be ‘have you had sex?’ -Male participant, 21, Vulindlela
Social Desirability	Invasion of Privacy	Participants expressed worry about the lack of confidentiality and the possibility that the interviewer may tell others.	P: “Ok, I have nothing to hide, yeah but someone else would feel uncomfortable.” […] P: “Because it’s like you are invading their privacy and stuff like that, maybe they don’t even trust if you [the interviewer] that will not go outside and tell people that yhoo that one has 10 partners […]” -Male participant, 21, Cape Town, SA
	Managing impressions	Participants expressed worry about what others might think of them due to implied or overt stigma	P: Yes, there are some men who don’t want people to know that they practice anal sex. I: Only men? Is there any other way that men can practice sex besides anal sex? P: I mean guys who practice “both.” I: So you mean a guy who is bisexual or straight but practice anal sex with their girlfriend, for insist? P: Both actually. But especially straight guys, they don’t want to admit it. -Male participant, 23, Cape Town P:[Laughs] “someone would not want to choose 100 because they would feel like people will say they already have HIV but the question says what are your chances of getting HIV.” […] P: “They wont feel comfortable, they will think that the interviewer will think that they sleep around.” -Female participant, 20, Cape Town
	No social script for how to respond	For heterosexual women, asking questions about anal sex is not in accordance with social and cultural norms	P: “I don’t have a problem with it, it’s easy for me to answer it because I don’t do anal sex, but I think someone who does it will be a little bit uncomfortable because as I said people like me don’t believe in anal sex…but maybe someone who does it knows that the people who don’t do it, let’s say if I was a guy and I was interviewed by another guy and the interviewer is straight (does not do anal sex) and then he asks if I ever did anal sex, it would not be easy for me to answer because I know in our culture, community, and according to our parents it is wrong to do so, so I would be uncomfortable even though maybe I know I am bisexual, maybe I am not gay, I have a girlfriend but I do anal sex, I would be uncomfortable even if I think it’s right, but I would be knowing that people think it’s wrong.” -Female participant, age unknown, Vulindlela
Estimation of risk involves estimation of partner behavior and trust	Partner trust impacts risk perception and risk behavior particularly for young women-tension between behavior as the cause of risk and impact of partner behaviors on risk	Chances/percentages of HIV depend on partner trust Condom use depends on trust	P: “It is asking me what I think my chances of getting HIV are. I choose number four because I trust myself and I have only one partner. I do not cheat on my partner, I would get HIV if he would cheat on me.” -Female participant, 20, Vulindlela P: “Because that’s [choosing 40 or 50% risk] when there is no trust in the relationship and maybe your partner has cheated on you before so that’s why there are greater risk of the person to be affected by the virus.” -Female participant, 21, Vulindlela P: […] “If I don’t trust someone or they cannot give me an answer to a question of cheating then we have to use a condom when we have sex, that’s my way of protecting myself from them.” -Female participant, age unknown, Cape Town

P: Participant; I: Interviewer