Examination was performed in a group of 539 adult patients with diarrhea admitted to the Department of Infectious Diseases in Gdańsk from 1991 to 1994. The group of 17 patients with antibiotic-associated colitis (AAC) was analysed. The antibiotics responsible for AAC were lincosamides, cephalosporins and penicillins. AAC was diagnosed by anamnesis, medical examination and detection of toxin A Clostridium difficile in stool samples. The contrast enema, colonoscopy and histopathological examination of colon mucosa were performed only in severe, protracted cases. The course of disease was mild in 2 cases, moderate in 13 and severe in 2 patients. Relapses of AAC were observed in 2 cases. Initial treatment of AAC included discontinuation of the antibiotic therapy that precipitated the disease and the replacement of fluid and electrolyte losses. Moreover, oral metronidazole and oral vancomycin were administered. All patients made a complete recovery.