Respondent-driven sampling (RDS) was used to recruit both MSM and FSW in Swaziland. RDS is a peerreferral sampling methodology specifically designed to address the challenges in collecting rigorous, representative data within hard-to-reach populations (Heckathorn, 1997). In RDS, a small convenience sample of the population is first identified and recruited. These initial participants, known as “seeds,” are then asked to recruit other individuals from the target population, beginning a series of chainreferral sampling.