Methods	DESIGN: Multi-centre RCT
	LENGTH OF FOLLOW-UP: 6 and 12 months post-intervention
	DATA ANALYSIS: States intention to treat protocol with participants analysed in their original assigned study groups irrespective of the number of sessions attended. However, it does not appear that all randomised participants were analysed, as only 605 (85%) of the 715 randomised were included in the primary analysis at 12 months follow-up (289/ 83% in Group 1 and 316/86% in Group 2)
	ATTRITION RATE: Group 1 = 289 (83%) completed 12 month follow-up; Group 2 = 316 (86%) completed 12 month follow-up. No differences in retention observed at 6 months (P = 0.98) or 12 month (P = 0.28) assessment
	UNIT OF DATA ANALYSIS: Individual
	SAMPLE SIZE CALCULATION: Reported for primary biological outcome (20% reduction in incident chlamydial infections over 12 months, assuming 80% retention, type 1 error rate of 0.05, power = 0.80, requiring 700 participants)
	EQUIVALENT STUDY GROUPS AT BASELINE: The study groups appeared generally similar at baseline. There were few statistically significant differences between study groups on socio-demographic variables, sexual behaviour, STI status, psycho-social mediators or other covariates
	PROCESS EVALUATION: Attendance at experimental intervention/comparison sessions was recorded. Participants rated their satisfaction with session delivery and value of session content. Fidelity ofexperimental and comparison interventions rated by trained monitors
Participants	NUMBER RANDOMISED: 715
	AGE: Group 1 Mean = 17.79 (SD 1.71); Group 2 Mean = 17.78 (SD 1.73)
	SOCIO-ECONOMIC STATUS:
	Poor neighbourhood quality: Group 1 = 0.58 (SD 0.93), Group 2 = 0.62 (SD 0.95)
	Family aid index: Group 1 = 0.78 (SD 0.95); Group 2 = 0.91 (SD 1.07)
	Employed, n (%): Group 1 = 106 (30.5); Group 2 = 104 (28.3)
	Currently in school, n (%): Group 1 = 230 (66.1); Group 2 = 237 (64.6)
	ETHINCITY/RACE: Eligibility criteria specified identifying as an African-American
	LOCATION: Clinics providing sexual health services to predominantly inner-city adolescents located in downtown Atlanta, Georgia, USA.
	PREVIOUS STI: Approximately 46% of the participants had an STD at baseline chlamydia n (%): Group 1 = 110 (31.6); Group 2 = 107 (29.2)
	Gonorrhoea n (%): Group 1 = 51 (14.7); Group 2 = 48 (13.1)
	Trichomoniasis n (%): Group 1 = 72 (20.7); Group 2 =60 (18.0)
	SEXUAL RISK BEHAVIOUR:
	Condom use in past 14 days, mean (SD): Group 1 = 50.42 (44); Group 2 = 53.29 (45)
	Condom use in past 60 days, mean (SD): Group 1 = 51.00 (41); Group 2 = 52.22 (41)
	Consistent condom use in past 14 days, No (%)*: Group 1 = 97 (35.1); Group 2 = 128 (41.6)
	Consistent condom use in past 60 days, No (%)*: Group 1 = 69 (23.1); Group 2 = 86 (27.2)
	Condom use during last sex, No (%)*: Group 1 = 152 (43.9); Group 2 = 153 (41.7)
	Casual sex partner, No (%)*: Group 1 = 105 (30.2); Group 2 = 120 (32.7)
	In past 60 days number of vaginal sex partners, mean (SD): Group 1 = 1.54 (1.38);
	Group 2= 1.60 (1.44)
	In past 60 days number of times having vaginal sex, mean (SD): Group 1 = 13.08 (16.
	63); Group 2= 11.90 (14.36)
	OTHER:
	* percentages do not appear to have been calculated on the total number randomised
Interventions	NAME OF STUDY:
	GROUP 1: STI/HIV risk reduction intervention (Horizons) (n = 348)
	YEAR STARTED: March 2002 to August 2004
	PROVIDER(S): African American women health educators
	SETTING(S): Sexual health clinic
	TYPE: Information/education on STD/HIV risk reduction. Practical skill development (condom use skills, negotiation skills). Provision of resources (vouchers for females to give to their male sexual partners to facilitate access to STD screening/treatment)
	DURATION: 2 x 4 hour sessions over 2 consecutive Saturdays (on average 8 participants attending each session). 4 x brief (15 minute) telephone contacts: 1 contact 3 to 4 weeks following completion of baseline assessment; a second contact 10 to 12 weeks following baseline assessment, a third contact 3 to 4 weeks following the 6 month follow-up assessment and final contact 10 to 12 weeks following the 6 month follow-up assessment
	THEORETICAL BASIS: Social cognitive theory, Theory of Gender and Power
	STIs COVERED: STIs in general/HIV
	GROUP 2: Enhanced usual care comparison (n = 367)
	YEAR STARTED: As Group 1
	PROVIDER(S): As Group 1
	SETTING(S): As Group 1
	TYPE: Information/education on STD/HIV risk reduction
	DURATION: 1 hour group session
	THEORETICAL BASIS: Not stated
	STIs COVERED: STIs in general/HIV
Outcomes	PRIMARY: Primary biological outcome measure was number of incident chlamydial infections at 6 and 12 month assessments. Primary behavioural outcome was the proportion ofcondom protected sex acts in the 60 days prior to 6 and 12 month assessments
	SECONDARY:
	Incidence of gonorrhoea and trichomoniasis. Number of lifetime sexual partners, condom use at last sex, consistent condom use, frequency of douching. Knowledge of STD/ HIV prevention, condom use self-efficacy, communication frequency
Notes	COST DATA: Not reported (other than women were given $20 vouchers to give to their male partners to redeem at clinics for sexual health services)
Risk of bias
Bias	Authors’ judgement	Support for judgement
Adequate sequence generation?	Low risk	Used a computer algorithm to generate random allocation sequence
Allocation concealment?	Low risk	Assignment adhered to concealment of allocation procedures defined by protocol and compliant with published recommen-dations, using opaque envelopes
Blinding? All outcomes	Low risk	For self-reported outcomes (e.g. sexual behaviour) data collectors (Audio Computer Assisted Self Interview monitors) were blind to participants condition assignment. Not reported whether those analysing vaginal swabs for STIs were blinded to intervention assignment, but as this could be considered a more objective outcome measure the lack of blinding may not pose a great risk of bias
Incomplete outcome data addressed? All outcomes	Low risk	Attrition was generally balanced between the two study groups (retention at 12 months follow-up was 83% to 86%). Reasons are specified and appear balanced between groups. It is stated that there were no differences for variables at baseline for participants retained in the trial compared to those unavailable for follow-up
Free of selective reporting?	Low risk	Results for all outcomes specified in the methods section of the trial publication are reported, with the exception of lifetime number ofpartners (which was a secondary outcome)
Free of other bias?	Unclear risk	Unclear