The current study was designed to determine the age at which menarche occurs among school girls in Madina, Accra. A survey was conducted among 529 girls selected using multi-stage sampling from basic schools in Madina, Accra. Respondents completed a questionnaire that recorded age-at-first menstruation by recall, household characteristics, and anthropometry. Mean age at menarche was 12.74 +/- 1.15 years; probit analysis yielded a median age of 12.09 years. Menarcheal age was significantly correlated with current age (r = 0.48; p < 0.01). Most girls (90%) had first menstruation before age 13. Their mothers' mean age at menarche was 13.6 +/- 1.08 years. In a multivariate linear regression model, household wealth (p < 0.01) and body mass index (p < 0.01) were the main modifiable independent predictors of age at onset of menarche. School girls in Madina attained menarche earlier than previously estimated. Our study suggests an influence of household level improvement in socio-economic status on menarcheal age.