Circumcision seems to reduce the overall incidence of urinary tract infections (UTI), although a few studies have suggested that ritual circumcision may be a predisposing factor for UTI within the first 2 weeks following the procedure. The aim of this study was to investigate a possible causal relationship between ritual circumcision and UTI. The study comprised 82 infants with UTI, 55 females and 27 males under the age of 1 year. All males were circumcised on the eighth day of life. The median age of infection was 0.75 and 7.0 months for males and females, respectively. Fifty-two percent (14/27) of UTI episodes were diagnosed within the 2 weeks following circumcision. A significantly lower incidence in Escherichia coli-induced UTI was observed in males compared to females, 67% and 93%, respectively. Similarly, the incidence of E. coli-induced UTI was also significantly lower in males presenting within 2 weeks following circumcision (57%) compared to infants presenting prior or more than 2 weeks following the procedure (92%). Positive blood cultures of an identical microorganism were observed in 6/27 males compared to 2/55 females. The incidence of urinary tract malformations and their severity were similar in both sexes. We conclude that the high incidence of UTI following a ritual Jewish circumcision, as well as the relatively high preponderance of bacteria other than E. coli, may suggest a causal relationship between circumcision and UTI.