The mean age at menarche in 6252 girls from secondary schools in 6 areas of the Veneto (Northern Italy) in 1975-1976, was estimated by probit analysis as 12.77 .+-. 0.038 yr. This mean is the highest known for Italy. Sexual maturation appears late in girls from large families and early in girls from small families: mean menarcheal ages were respectively 12.81 .+-. 0.057 and 12.64 .+-. 0.036 yr.