A retrospective case-controlled study was performed in 36 Thai children with Plesiomonas shigelloides (P. shigelloides)-associated diarrhea admitted to the Department of Pediatrics, Faculty of Medicine, Siriraj Hospital, Mahidol University from August 1990 to December 1992. Nineteen cases received antibiotics while seventeen did not receive any. The two groups were comparable in age, sex, duration of fever, duration and severity of diarrhea and medical treatment. The antibiotics given were norfloxacin, wintomylon, colistin, gentamicin, ceftriaxone, co-trimoxazole and ampicillin. In our study, 100% of P. shigelloides isolates were susceptible to quinolones and cephalosporins, while only 9% were susceptible to ampicillin. Co-trimoxazole, gentamicin, netilmicin, chloramphenicol and nalidixic acid showed high susceptibility. The duration of fever and diarrhea after treatment was not significantly different between treatment and control groups (p > 0.05). Therefore, we conclude that antibiotics did not change the duration of fever and diarrhea in Thai children with P. shigelloides-associated diarrhea.