Purpose: the authors evaluated shape and retracability of the preputial in school boys from 6 to 14 years old. Material and method: cross-sectional study, include 536 school boys from 6 to 14 year old in Phu Luong distric, Thai Nguyen pvroince. Preputial status was evaluated acording to Kayaba classification. Results: The incidence preputial status from type I to type V was 8,4 percent, 9,9 percent, 23,3 percent, 26,9 percent, 31,5 percent, respectively. The incidence of a completely retractable prepuce (type V) gradually increased from 15.5 percent at age 6 years to 62.9 percent by 16 years, while that of a tight ring (type I) decreased with age, from 11.3 percent at age 6 years to 2.2 percent by 14 years. 14,7 percent boys had balanoposthitis. Conclusion: Incomplete separation of the prepuce is common in school boy, and preputial separation progreses until adolescence.