Somatostatin analogs are an alternative treatment to pituitary surgery and radiotherapy in acromegalic patients. Recently, a depot long-lasting formulation of slow release (SR) lanreotide has been shown to be effective in the short-term control of GH hypersecretion in acromegalic patients. We report the long-term follow-up of a cohort of 22 acromegalic patients treated with SR lanreotide during 1-3 yr. Thirteen females and 9 males, age 51 +/- 3 yr, presented with macroadenomas (n = 12), microadenomas (n = 8), or empty sella (n = 2). Seven patients previously had undergone a partial surgical removal of their adenomas, and 21 of them had mean plasma GH levels less than 5 micrograms/L during a previous octreotide treatment. According to GH values recorded after 3 months of twice monthly 30 mg SR lanreotide im injection, SR lanreotide was administered every 14 days (n = 13) or every 10 days (n = 9). At the 6-month visit, mean GH values were 5 micrograms/L or less in 68% and 2.5 micrograms/L or less in 27% of patients, and these results remained unchanged during the 1-3 yr follow-up period. During SR lanreotide treatment, the mean insulin-like growth factor I (IGF-I) concentrations remained in the normal range in 63% of patients. No escape from the treatment occurred in any of the cases. A significant decrease of the pituitary tumor volume was observed in 3 (13%) patients. The main side effect consisted of minor digestive problems during 48 h after each injection and was reported by 13 patients. Biannual gallbladder echographies revealed the occurrence of gallstones in 4 (18%) patients. In conclusion, these data confirm the efficacy and the tolerance of the long-term SR lanreotide administration (30 mg im every 10-14 days) in the control of acromegaly.