An optimized reusable hollow fiber ultrafiltration system (50,000 MWCO) was developed to concentrate Cryptosporidium oocysts from 10 L samples of environmental water. Seeded experiments were conducted using a number of surface water samples from the southwest. Ultrafiltration produced a mean recovery of 47.9% from 15 water samples (55.1% from 39 individual tests). These results indicate that hollow fiber ultrafiltration can efficiently recover oocysts from a wide variety of surface waters and may be a cost effective alternative to concentrate Cryptosporidium from water given the reusable nature of the filter. Includes 12 references, tables, figure.