The present study was conducted to investigate the epidemiological characteristics such as isolation rate and antimicrobial drug susceptibility of etiological agents. The specimens (stool or intestine) were collected from 319 calves with clinical diarrhea from 195 farms in Gyeongnam south area (Gosung, Tongyung, Hadong) from June 2005 to August 2006. The isolation rate of Salmonella spp was higher in summer (8.4%) than in winter (4.8%) and the average was 7.2% (23/319 head). Some of Salmonella spp isolated were resistant to penicillin, oxytetracycline, tetracycline, and cephalexin (>90%), but some of them were susceptible to norfloxacin, ciprofloxacin, sulfamethoxazole/trimethoprim and amikacin(>30%). There was no statistical difference in the isolation rate of Eimeria spp between summer(48.9%) and winter(42.3%). For the evaluation of infection level of Eimeria spp oocyst per gram of feces (OPG) was examined, and severe, moderate and light infection level were 11.9%, 12.5% and 22.3%, respectively. In the isolation rates of Eimeria spp the calves under 19 days was lowerthan those over 60 days, but there was not different among herd size.