The clinical and follow-up data of the isolated premature thelarche are reviewed in a series of 61 girls aged 6 months to 6 years. Transitory increase of plasma estrogens was observed in some cases. The results of LHRH test were similar to those from normal girls of the same age. Premature thelarche could be a normal variant in girls, related with the physiologic unsteadiness of the prepubertal female pituitary-gonadal axis.