Objective   To explore tendency and influencing factors of menarche age in Mongolian students and to provide a sugg estion for sexeducation for students.

  Methods   The results of investigation on body constitution of Mongolian students aged 7~18 in 2000 were compared with those in 1985.Probability unitreg ression and multiple regression methods were used to analyze the relationship between average menarche ag e, sexdevelopmentand body constitution.

  Results   From 1985 to 2000, average menarche ages were 0.81 year and 0.72 yearin advance in urban and rural areas respectively, which implied 0.54 and 0.48 yearin advance in urban and rural areas respectively.which implied 0.54 and 0.48 yearin advance per 10 years in urban and rural areas respectively.There were no significant differences for menarche age between Mongoliand and Han students.The menarche age was significantly related with body weight, Ver weck index, vital capacity, vital capacity/chestcircumference indexin the students of urban, and significantly related with weight, vital capacity, vital capacity/chestcir cumference index, body heightand pulse in the students of rural areas.

  Conclusion   There were sig nificant relationship between menar cheage and body constitution.Menarcheage showed an ahead trend of being in advance in Mongolian students of urban and rural area.Sexeducation should be conducted in advance, and itwas importantof streng then sexeducation in adolescent.