Abstract: Investigation on the menarchal age of 4 groups in Huhchot region were made in 1987, 1990, 1993, respectively. Statistics were made in groups arranged according to birth year and menarchal year. Results show that: 1)The process of moving up of MMA of girls born during 1963-1972 of both nationalities in Huhchot is quicker in recent years. The process of moving up of MMA of urban girls born after 1972 slowed down, but that of rural girls is still quicker; 2)The process of moving up of MMA of rural girls born during 1963-1977 is slightly higher than that of urban ones; 3)MMA of Mongol girls is usually earlier than Han who live in the same environment; 4)Statistics of data of 1993 by status quo method and retrospective method showed that the MMA of both nationalities in Huhehot has already reached the level of economically developed large cities in China and has been near to the lowest limit of MMA controled by genetic factors.

Key words: Menarcheal age; Mongol nationality; Han nationality