Entering puberty is one of the most important milestones in life. Studies from around the world have shown that age of pubertal changes onset can vary with race and ethnicity, environmental conditions, geographical location and nutrition. In the last century, the onset of puberty progressively shifted back towards younger ages in several European countries, with a levelling off in the last decades. The aim of our study was to describe the prevalence of secondary sexual characteristics in a group of children living in Northern Italy comparing them with the percentile values published by Tanner in 1976. We enrolled 3496 children drawn from public schools and evaluated height, weight and pubertal stages. The analysis of our data evidenced that the 50th percentile age of puberty onset in both sexes decreased by about 1 yr compared to data published by Tanner. Mean body mass index (BMI) z-score was significantly higher (p = 0.01) in pubertal than in pre-pubertal girls, on the contrary it was higher (p = 0.005) in pre-pubertal than in pubertal boys. In conclusion, our study found that girls and boys of our region are beginning pubertal development about 1 yr earlier than Tanner's British population. Taking into consideration the 3rd percentile age for Tanner's breast stage 2 in girls and testicular volume (TV) of 4 ml in boys, the current internationally used cut-off age for precocious puberty, i.e. 8 yr for girls and 9 yr for boys, can be maintained in our population.