Cryptosporidiosis species were demonstrated in stool of 1.9% of 1600 unselected patients with enteritis (practically evenly divided between children and adults). Further investigations revealed seven cases of enteritis among family members. In eight patients there was a double infection with Cryptosporidium plus another enteritis pathogen. The most frequent clinical symptoms were diarrhea, vomiting, cramp-like abdominal pain, fever and headache. The mean period of parasite excretion was 14 days. Spontaneous cure occurred in all patients. Since cryptosporidiosis is relatively common not only in those with lowered resistance but also those who are immune-competent, search for Cryptosporidium should be included in all tests for etiologically uncertain cases of enteritis.