The presence of Cryptosporidium spp oocysts was determined in seven samples of crude surface water and seven of treated non-chlorinated water from a water plant in San José,Costa Rica. Concentration and staining techniques were used to demonstrate the presence of parasites. Cryptosporidium spp oocysts were found in six of seven untreated water samples (85.7%) and in four of the seven treated non-chlorinated samples (57%). The role of water as a transmission vehicle for this parasite in Costa Rica is discussed.