In a two-part study of the circumcision status of boys with urinary tract infections (UTIs), we reviewed the occurrence of UTIs in 209,399 infants born in US Army hospitals worldwide from 1985 to 1990. During the first year of life, 1,046 (0.5%: 550 girls and 496 boys) were hospitalized for UTIs. Noncircumcised male infants had a 10-fold greater incidence of infection than did circumcised male infants. The frequency rate of circumcision rose significantly, from 70.3% to 80.2%, during the study period. Among uncircumcised boys younger than 3 months with UTIs, 23% had concomitant bacteremia involving the same organism. The second part of the study consisted of a meta-analysis of all nine previous reports on the circumcision status of boys with UTIs. These studies revealed a fivefold to 89-fold increased risk of infection in uncircumcised boys; the combined data yielded a 12-fold increase in UTIs in this population. Parents should be told of the lower risk of UTIs for circumcised boys during informed-consent counseling.