We offer a nationwide analysis of the initial years of Costa Rica’s PSA program, which pioneered environmental-services payments and inspired similar initiatives. Our estimates of this program’s impact on deforestation, between 1997 and 2000, range from zero to one-fifth of 1% per year (i.e., deforestation is avoided on, at most, 2 out of every 1,000 enrolled hectares). The main explanation for such a low impact is an already low national deforestation rate. We also consider the effect of enrollment. Predicted deforestation on enrolled versus nonenrolled hectares, and matching analyses suggest an enrollment bias toward lower clearing threat. Enrolling land facing higher threat could raise payments’ impact on deforestation.