The clinical picture and epidemiologic characteristics of infection due to Campylobacter fetus subspecies jejuni were studied in 188 patients hospitalized in Finland during a three-year period. All but two patients had diarrhea; 90% had abdominal pain, fever, and fatigue; half had vomiting and headache; one third experienced electrolyte disturbances; and one fifth of the patients had other complications, most commonly pancreatitis (6%) and arthritis (5%). All age groups were affected, most usually those who were 0 to 9 years old and 20 to 29 years old. The incidence of domestic cases increased during the summer months. With only three exceptions (1.3%), all jejuni strains were sensitive to erythromycin. Among Finns who visited ten popular tourist countries, the incidence of hospitalized C jejuni enteritis cases varied from 0 to 63 per 100,000 travelers.