In 142 Swiss girls of the First Zurich Longitudinal Study. The somatic pubertal development between 9 and 18 years is described. The mean chronological age at the onset of the pubertal growth spurt was 9.6 years (standard deviation 1.2 years). The peak of the pubertal growth spurt (peak height velocity: PHV) was reached at a mean age of 12.2 years (SD 1.0). The development of pubic hair started at a mean age of 10.4 years (SD 1.2), breast development at 10.9 years (SD 1.2) and the development of axillary hair at 12.0 years (SD 1.1). Menarche occurred 2.7 years (SA 1.1) after the initiation of pubic hair development and 2.2 years (SD 1.1) after the breast development had started. Menarche was noted at a mean age of 13.4 years (SA 1.1). At menarche the mean height was 156.9 cm (SD 6.3), the mean weight 45.5 kg (SD 6.8) and the mean bone age (according to Greulich and Pyle) 12.6 years (SD 0.8). With the onset of menarche 95.3% (SD 1.7) of adult height were reached; the corresponding remaining height gain was 7.8 cm (SD 2.8). Acne was observed in 81% and striae in 41% of the girls by 18 years.