Background: Respondent-driven sampling (RDS) is a peer-referral sampling methodology used to estimate characteristics of hard-to-reach groups that cannot be randomly sampled. RDS has been implemented in several settings to identify hidden populations at-risk for HIV, but few studies have reported the methodological lessons learned on RDS design and implementation for assessing sexual risk behaviors in vulnerable youth. Methods: We used RDS to recruit 362 young adults, aged 18 to 22, who were living in urban slum settlements in Nairobi, Kenya. Twenty seeds were selected and asked to recruit up to three eligible peers. The study used a 3-day recruitment coupon with sequential numbers to link recruiters to their recruits. Data collection was completed in 2 weeks with a maximum chain length of 6 waves. Results: RDS was effective in overcoming feasibility concerns of more traditional sampling methodologies. Recruit network sizes and selection probabilities varied considerable, as did relationships to recruiters. RDS benefits were high identification rates (i.e., number of coupons returned per coupons given), high eligibility rates (i.e., number eligible recruits per coupons returned), high efficiency (i.e., number of eligible recruits per days elapsed), and low screening threshold (i.e., number screened recruits per enrolled youth). Lower participant acquisition costs and increased inclusion of ethnic minorities were also observed. Operational challenges were unproductive seeds, coupon misuse, pace, involuntariness, and acceptability among women. Adaptations made to optimize RDS are also discussed. Conclusion: RDS may serve as an important tool in reaching a diverse sample of urban youth who are at-risk for HIV.