Menarche is a critical transition and biological event for women. Age at menarche is an important variable for women's health and appears to be decreasing from generation to generation. This study describes the distributions of recalled age at menarche of women in three-generation families, examines generational differences, and evaluates the effects of birth mothers' and birth grandmothers' recalled age at menarche on their daughters. This cross-sectional investigation was performed on 214 post-adolescent girls from central Taiwan and their birth mothers and grandmothers. The descriptive analysis, analyses of mixed effect models, and multiple linear regression analyses were employed to examine the relationships of age at menarche for three generations within families. The distribution of age at menarche moved significantly earlier over the three generations. The mean ages at menarche were 15.16 +/- 1.75, 14.50 +/- 1.50, and 13.00 +/- 1.26 years for grandmothers, mothers, and daughters, respectively. Four factors for the daughters' age at menarche (adjusted for age at the time of the study and geographical location) were identified. The first three were reinforcing effects. These were the product of the mothers' and grandmothers' ages at menarche, the product of the mothers' geographical locations and ages at menarche, and the product of the grandmothers' ethnicity and ages at menarche. The fourth factor was the grandmothers' ethnicity. The results showed a significant decrease in the onset age of menstruation over three generations, with a positive effect on age at menarche from mothers to daughters and from grandmothers to granddaughters.