The possible association of urinary tract infection (UTI) with ritual circumcision on the eighth day of life was studied by analyzing the epidemiology of urinary tract infections during the first year of life in 169 children with UTI (56 males and 113 females) born in Israel from 1979 to 1984. Forty-eight percent of the episodes of UTI occurring in males appeared during the 12 days following circumcision, and the increased incidence during that period was highly significant. The median age of the males at the time of the UTI was 16 days, compared with seven months in females. Ritual Jewish circumcision as practiced in Israel may be a predisposing factor for UTI during the 12-day period following that procedure.