The presence of various enteropathogens was examined in the feces of homebred dairy calves reared in a restricted geographical area of France (North West of County of Indre-et-Loire) during winter 1983-1984. Two distinct surveys were carried on: a case-control study including 32 diarrheic calves and 21 healthy calves bred in 53 different farms; and a separate study on nine diarrheic calves in another farm. The following infectious agents were looked for, by specific methods of detection: Escherichia coli K99 and E. coli lethal for mice, Salmonella species, Yersinia enterocolitica, Campylobacter jejuni, enterotoxigenic Clostridium perfringens, Chlamydia psittaci, rotaviruses, coronaviruses, Cryptosporidium. In the case-control survey, no enterotoxigenic E. coli (K99+) was detected in either group of calves. Four agents were more often detected in diarrheic calves than in healthy calves, i.e. rotavirus (12/32 vs 1/21), lethal E. coli (6/32 vs 1/21), Cryptosporidium (2/32 vs 0/21) and Salmonella typhimurium (1/32 vs 0/21). One at least of these four agents was present in 16 diarrheic calves (50%) vs only 2 healthy calves (10%) (P less than 0.01). On the other hand, the occurrence of Campylobacter jejuni and of C. perfringens, enterotoxin was similar in both groups of calves, accounting respectively for about 20% and 10% of total calves. Moreover, coronavirus-like particles were significatively associated with healthy calves (7/32 vs 11/21; P less than 0.05). In the other study, all the main categories of enteropathogens were detected throughout the period of observation in the same farm with the exception of enterotoxigenic E. coli. But each calf taken individually was rarely shedding more than two agents at a time. In addition, specific antibodies against C. perfringens enterotoxin, as tested in an ELISA test, were present in the serum of all the calves examined in both surveys. This study confirms the primary role of rotavirus and Cryptosporidium as agents of diarrhea in calves under three weeks. It also suggests the possible participation of E. coli strains that are lethal for mice and underlines the potential hazard for human health of bovine reservoirs of Campylobacter jejuni and enterotoxigenic C. perfringens.