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Objectives. To determine the mean age of pubertal stages of breast development and menarche, and the influence of nutrition and ethnicity on pubertal onset in primary school girls in Sokoto, North-Western Nigeria.

Methods. A cross-sectional study using a multistage random sampling design was conducted on 994 primary school girls in grades 3-6. Weight and height measurements and Tanner breast staging were done. Body mass index (BMI) was calculated, and a BMI-for-age percentile was used to categorise nutritional status. There were four major ethnic groups. P≤ 0.05 was taken as showing statistical significance.

Results. The participants’ mean age was 10.23 years (standard deviation (SD) 1.70, range 6-15 years). Of the 994 girls, 628 (63.2%) were pre-pubertal, and 366 (36.8%) were pubertal. Of the latter, 158 (15.9%) were in breast stage 2, while 112 (11.3%), 70 (7.0%) and 26 (2.6%) were in breast stages 3, 4 and 5, respectively. The mean ages (SD; range) of pubertal onset and menarche were 10.50 (1.33; 8-13), and 12.67 (1.65; 11-15), years, respectively. The overnourished (overweight/obese) and Igbo ethnic group girls had early-normal pubertal onset (p= 0.006 and p= 0.001, respectively).

Conclusion. The mean ages of Tanner breast stages 1-5 and menarcheal age of girls in Sokoto, North-Western Nigeria, were within the age ranges reported worldwide. Pubertal onset was influenced by nutrition.