From September 1986 through July 1987, all fecal specimens obtained from infants and children who visited the pediatric clinic of the Shizuoka General Hospital with complaints of abdominal pain or diarrhea were examined for thermophilic Campylobacters. Bacteriological and epidemiological studies were performed on household contacts. The mothers of the patients were compared with the mothers of age-matched control subjects. Bacteriological examination of animals in 49 primary schools in Shizuoka city was performed.<BR>C. jejuni was isolated from 47 (9.4%) of the 499 feces samples, occupying first place in the bacterial etiology of acute bacterial enteritis. Infants and young children below 10 years of age comprised 81% of the total cases. Fourteen (13%) strains of C. jejuni were isolated in 9 families among 105 household contacts of the index patients.<BR>Six symptomatic contacts in two households had eaten the same suspected chicken as the respective index patients. In three families, C. jejuni was isolated from the remainder of the chicken. The serotype of these isolates was identical to that of the isolates from the index cases and the other family members. It was also noted that the same chopping boards were used for the preparation of salads after cleansing with water. In two index cases, the antibody of convalescent serum against C. jejuni isolated from the chicken, as estimated by passive hemagglutination method, ranged from 1: 320 to 1: 1280. These facts strongly supported the assumption that they had been infected by the chicken. The remaining persons were asymptomatic and the possibility was left that the index cases had been secondarily infected by these carrier persons. The serotype of 42% of the 26 human isolates was type 2, according to the schemes of Penner. The predominance of type 2 was also observed in commercially available chicken in Shizuoka city.<BR>In a case control study, the incidence of consumption of chicken, beef and pork was essentially the same in both groups. However, a significantly small number of mothers washed the chopping board or kitchen knife with a cleanser after cutting raw meat. There was no significant association with the keeping pet animals.<BR>862 animals (251 chickens, 498 cage birds and 113 rodents) were kept in forty-nine primary schools. Three hundred and thirty-nine animals were examined. Two chickens and 5 cage birds had Campylobacter in their feces. Some of them showed signs of illness. However, long term carriage was rare and no children suffering from diarrhea were observed among animal breeders. It is already clear that in Shizuoka city, the majority of chicken carcasses sold at markets are contaminated by C. jejuni.<BR>We conclude that in Shizuoka city, the important factor in the transmission of Campylobacter is handling of raw poultry, and subsequent cross-contamination of hands, surfaces and other foods. Careful washing of the hands and kitchen knives with water and soap or a cleanser after handling raw poultry, and the avoidance of the common use of a chopping board for raw meat and salads will greatly reduced the risk of transmission.