In 1970 a study was made of 354 girls 10 to 17 years old, who attended 2 private and 5 public schools in Santiago, Chile. The age of menarche calculated by the probit method was of 12.6 years for the total group. On comparing these results with those obtained by other authors in other Latin American and Western European countries, the similarities were striking in spite of the differences in economic development that exist among the samples. On subdividing our sample by socioeconomic level, age of menarche was lower in girls of worse socioeconomic status (12.3 years), than in those of high status (12.97). The total sample was partitioned into subgroups, according to the number of foreign grandparents and to the presence or absence of shovel shape incisors. It was observed that among the girls with a greater number of foreign grandparents as well as among those with shovel-shape teeth the age of menarche was higher than among those, with no foreign grandparents (12.8, 13.0 and 12.4 years respectively). It is postulated that the groups with a greater or smaller degree of indigenicity are those with a higher age of menarche, although the meaning of this fact is not clear. Age of menarche was analized according to the amount of subcutaneous fatty tissue, measured with a caliper in the sub-tricipital, subscapular and subcostal regions. It was observed that menarche ensued significantly earlier in girls with more subscapular or subcostal adipose tissue. This was not observed in respect to tricipital subcutaneous tissue.