This paper discusses the social impactsof Costa Rica's Payments for Environmental Services(PSA) program and their effect on rural poverty. Althoughthe analysis is hampered by significant information gaps, webelieve that the PSA Program has probably managed to have animpact on the poor. This impact is almost certainly positiveon the poor who were able to participate, but is difficultto quantify. However, except for very few cases, it seemsunlikely that the PSA was able to actually lift participantsout of poverty. Participation of the poor was initially lowbut increased as measures were introduced to target the poorand facilitate their participation.