This paper reviews the clinical findings, pituitary gonadotrophin reserve and plasma oestradiol, neurological findings and pelvic ultrasound appearance in 47 girls with precocious puberty starting before the age of 7 years. Of the 39 girls who had air encephalograms or cranial CT scans, 19 showed intracranial abnormalities (hamartomas 11; hydrocephalus 5; optic glioma 2; arachnoid cyst 1). There was no significant difference in the peak serum luteinizing hormone and follicle-stimulating hormone responses to intravenous gonadotrophin stimulating hormone in girls with and without intracranial lesions. Pelvic ultrasound examination showed development of the ovaries, uterus, and vagina similar to that seen in normal puberty. Treatment with cyproterone acetate (50-100 mg/day) in 26 girls resulted in arrest of breast development and suppression of menstruation, but a definite effect on growth was not documented.