To determine menarcheal and pubertal ages and possible factors responsible for current pubertal trends in Kumasi, Ghana, a cross-sectional study was conducted among 720 urban and rural Kumasi 7-17-year-old schoolgirls and their mothers in 2008. Heights and weights were measured and additional information obtained by survey. Mantel-Haenzsel, χ(2), ordered logistic regression and probit analyses were used to analyse the data collected. With 40.42% menarcheal prevalence, median menarcheal ages were significantly different: 12.37 ± 1.48 years urban and 13.41 ± 2.25 years rural; 12.89 ± 1.93 years, overall. Obesity (OR = 2.57; p = 0.033) and high socioeconomic status (OR = 2.12; p = 0.008) were predictors of early menarche, while a younger mother was protective against early menarche (OR = 0.32; p = 0.039). Age at menarche among Kumasi schoolgirls has dropped 0.76 years since it was last determined among similarly aged girls in 1986, declining at a rate of about 0.32 years/decade. The predicting factors provide an important opportunity for intervention through school curricula and targeted education of adolescents.