The purpose of this study was to investigate the cause of chronic diarrhea from anaerobic bacteria isolated from Siberian tiger with chronic diarrhea. Major anaerobic bacteria isolated from faces were Clostridium perfringens and their population was $6 { imes} 10^3$ cfu/g feces. Antibiotic sensi- tivity test against Clostridium perfringens was performed using 6 antibiotic drugs including colistin gentamicin, trimethoprim/sulfamethoxazole, amikacin, enofloxacin and penicillin. Clostridium per- fringens were sensitive to amikacin, enrofloxacin and penicillin while they were resistant to colistin. gentamicin and trmetboprim/sulfamethoxazole. And we found that chronic diarrhea of Siberian tiger was treated successfully with penicillin. These results suggested that Clostridium perfringens may bee a cause of chronic diarrhea in Siberian tiger.