Age of thelarche presentation, breast evolution, growth and puberty patterns were retrospectively evaluated in 119 girls with premature thelarche (PT). Thelarche spontaneously presented before 2 yr of chronological age in 80% of girls and completely regressed in 60% of them. Breast regression was significantly more frequent in the patients with more precocious thelarche presentation. In 40% of the girls breast size did not significantly change during a follow-up period ranging from 12 to 134 months (40.6 +/- 32.5). Among the 38 girls who were followed up to an age greater than 8 yr, seven (18.4%) developed central precocious puberty (PP). These 7 patients who progressed into true PP were indistinguishable from girls with normal puberty for age of thelarche presentation, breast size, evolution and auxological features. On the contrary, a subgroup of patients (28.5%) with accelerated height velocity and/or bone age at diagnosis of PT showed an auxological pattern different from normally growing girls during a 3-yr follow-up, but they did not seem to have higher risk of progressing into precocious puberty. In conclusion, PT encompasses different clinical, and perhaps hormonal situations, therefore requiring careful clinical follow-up.