The natural course of preputial development is still not clearly understood. The preputial retractability was evaluated in 242 Japanese boys. The incidence of having a retractable prepuce gradually increased with age from 0% at age 1 year to 77% by the age of 11 to 15 years. In 48 boys, preputial development was followed up for 2 to 10 years with the self-retract maneuver. Non-retractable prepuce was found in 9 boys, which then became retractable within 2-7 years. The prepuce became retractable in most of the boys with balanoposthitis. In conclusion, forced retraction or circumcision is unnecessary for phimosis in boys with or without balanoposthitis.