Fourteen patients with precocious puberty were treated for 1-3 years with 900-1800 micrograms/day of intranasal (i.n.) Buserelin. The peak luteinizing hormone and follicle-stimulating hormone responses to intravenous luteinizing hormone-releasing hormone were reduced significantly 4 weeks after starting treatment and remained suppressed while the patients were on treatment. Two patients were withdrawn because of drug non-compliance. Three patients showed regression of pubertal changes, four patients showed no progression and five patients showed progression of breast size or pubic hair staging after 1.5-2 years of treatment. Treatment was changed to the subcutaneous route in two patients because of hormonal escape and accelerated skeletal maturation. The mean growth velocity decreased from 10.78 cm/year (s.e.m. = 0.64) to 7.06 cm/year (s.e.m. = 0.85) after 1 year of treatment (P less than 0.005). After an increase in dosage (from 900 micrograms/day to 1800 micrograms/day) in most patients, further significant falls in growth velocity to 5.29 cm/year (s.e.m. = 0.45), 4.63 cm/year (s.e.m. = 0.8) and 5.06 cm/year (s.e.m. = 0.5) were observed at 18, 24 and 30 months, respectively, compared with the pretreatment value (P less than 0.001). With treatment, the increased rate of skeletal maturation normalized. In 10 patients who had completed 2 years of treatment, the height standard deviation score for bone age improved from a pretreatment value of -2.42 +/- 0.42 to -1.6 +/- 0.42 after 2 years of treatment (P less than 0.01), indicating an improvement in height prognosis. It is concluded that i.n. Buserelin at a dose of 1800 micrograms/day is effective in the treatment of most but not all patients with precocious puberty.