The influence of puberty on sweating patterns of girls exercising in the heat is not known. Nine- to 17-year-old girls, representing 4 stages of breast development: T1 (
n= 21); T2 ( n= 22); T3 ( n= 25); and T4 ( n= 22), cycled for 20 min at 60% in 35 °C. The population density of heat activated sweat glands was higher in T1 vs T3 and T4 and in T2 vs T4. Sweat drop area was lower in T1 vs T3 and in T1 vs T4, T2 vs T4 and T3 vs T4. The proportion of skin covered by sweat was lower in T1 vs T4. Sweating patterns of girls exercising in the heat are influenced by pubertal stage.