Abstract: A survey of cryptosporidiosis in outpatients and inhabitants in Xuzhou city and 6 rural areas of Jiangsu Province was carried out from 1989 to 1991.Cryptosporidium oocysts(CSO) were found in 97((1. 6%)of 6 221 individuals as a whole, and were detected in 39 (3. 3%) of 1 172 outpatients among the examinees. 39 cases were from 31 towns and villages of 8 counties near Xuzhou city. Among the 136 cases,83 were males and 53 females,of them 89 (65. 4%)were infants and young children. The incidence was evidently higher in the group of children under 4 than in that aged 4 to 15(P0. 01). Diarrhea,intermittent or persistent,was the main symptom of cryptosporidiosis,being present in 94(69. l%)of the 136 positive cases, while the other 42 were asymptomatic carriers. The results of routine blood examination and immunoassay performed in a part of the infected children indicated that more than half of them had anemia and lessened cellular immunity. Stool examination of the domestic animals of the affected households showed that a pig and a dog were CSO positive.