The prevalence of penile problems was examined in a birth cohort of more than 500 New Zealand children studied from birth to 8 years of age. By 8 years, circumcised children had a rate of 11.1 problems per 100 children, and uncircumcised children had a rate of 18.8 per 100. The majority of these problems were for penile inflammation including balanitis, meatitis, and inflammation of the prepuce. However, the relationship between risks of penile problems and circumcision status varied with the child's age. During infancy, circumcised children had a significantly higher risk of problems than uncircumcised children, but after infancy the rate of penile problems was significantly higher among the uncircumcised. These associations were not changed when the results were adjusted statistically for the effects of a series of potentially confounding social and perinatal factors.