OBJECTIVE: To determine the feasibility and acceptability of conducting a community randomized trial (CRT) of an adolescent reproductive health intervention (ARHI) using biological measures of effectiveness. SETTING: Four secondary schools and surrounding communities in rural Zimbabwe. METHODS: Discussions were held with pupils, parents, teachers and community leaders to determine acceptability. A questionnaire and urine sampling survey was undertaken among Form 1 and 2 pupils. Studies were undertaken to inform likely participation and follow up in a future CRT. A community survey of 16-19-year-olds was conducted to determine levels of secondary school attendance and likely HIV prevalence at final follow up in the event of a trial. RESULTS: Form 1 and 2 pupils aged 12-18 years (n = 723; median age, 15 years) participated in the research. Prevalences of HIV, Chlamydia and gonorrhoea were 3.6% [95% confidence interval (CI), 2.3-5.3%], 0.4% (95% CI, 0.1-1.3%) and 1.9% (95% CI, 1.0-3.3%) respectively. There was poor correlation between biological evidence of sexual experience and questionnaire responses, due to concerns about confidentiality. Only 13% (95% CI, 4-27%) of those infected with HIV and/or a sexually transmitted disease admitted to having had sex. In the community survey of 573 adolescents aged 16-19 years, 6.6% (95% CI, 3.9-10.3%) of females and 5.1% (95% CI, 2.9-8.2%) of males were HIV positive. High participation and retention rates are achievable within a trial in this setting. CONCLUSIONS: It is acceptable and feasible to conduct randomized trials to establish the effectiveness of ARHIs. However, self-reported behavioural outcomes will probably be biased, emphasizing the importance of using externally validated biological outcome measures to determine effectiveness.