TABLE 1.

Results: Main Themes

Theme	Definition	Relevant Quote
Motivation	Receiving financial compensation was initially the main motivation and in some cases, the only reason, to enroll in the study.	“I am hustling, always hustling and I could really use that money.” (Participant C)
Coercion	The need to avoid the heroin withdrawal effects placed them in a relatively vulnerable position as prospective research participants.	“If one is sick [experiencing heroin withdrawal], desperate, it is true that the user can’t say “no”, you do whatever it has to be done.” (Participant I)
Trust	Participants recognize that money, while initially ensuring their participation, can’t by itself buy trust	“Trust has nothing to do with [payment]” (Participant K)
Reciprocity	Participants perceive financial compensation as an important step in the process of building trust.	“If you help me, you’re curing me, well, then I give you the information you need and then we both help each other.” (Participant L)
Cash payments	Participants have a mixed view on receiving gift cards instead of cash incentives.	“No, I wouldn’t do it because it is going to be very difficult to sell it” (Participant F). “A gift card is money, sure, with it I can buy something good” (Participant M)