Urinary tract infection (UTI) is one of the most commonly encountered infections in childhood. It has been demonstrated that the preputial sac can act as a reservoir of organisms and is thus responsible for causing ascending UTIs. This study was performed to determine the presence of preputial flora in different age groups. Prepuce and urine samples were taken simultaneously from 92 uncircumcised and healthy male children aged between 0-12 years. The data were analyzed by age, with 47 subjects of 6 years of age or less, and 45 aged 7-12 years. Twenty-seven percent of the older patients had negative preputial cultures versus 8% of those under 6 years of age (chi2 = 5.27, P = 0.02). In addition, enteric bacteria were the most common pathogens isolated from the prepuce in younger children while skin flora bacteria were most common in the older group (chi2 = 9.18, P = 0.002). The urine was sterile in all cases. Preputial cultures change with age in uncircumcised boys. This change may be related to the development of immune status, to histological or anatomical changes in the prepuce, and/or to improved personal hygiene.