Presented by Carl Kendall, Débora Aranha, and Elizabeth Anderson. The Freedom Fund’s PRIF project estimated the size of the population of female children and adolescents less than 18 years of age experiencing commercial sexual exploitation of children (CSEC) in the Recife Metropolitan Area (RMA) in Brazil. The study used 1) the Successive Sampling Population Size Estimation (SS-PSE) method via Respondent-Driven Sampling (RDS) among young women between 18 and 21 years of age who engaged in commercial sex and who began exchanging sex for money, favors, or goods or were otherwise commercially sexually exploited at least once before their 18th birthday, and 2) the Network Scale-Up Method with a random sample of RMA residents contacted by phone.