New depot somatostatin analogs such as lanreotide-slow release (LAN) represent a significant improvement in the medical treatment of acromegaly. Seventy-three consecutive acromegalic patients, treated by LAN, were evaluated in a retrospective monocentric study. Sixteen were excluded from further evaluation due to combined treatment with dopamine agonist drugs, early LAN withdrawal for persistence of headache, or gastrointestinal side-effects. Fifty-seven patients (aged 20-82 years, 16 males) were thus evaluated. Thirty-two patients had been previously treated by neurosurgery (Tx) and/or radiotherapy (Rx). After washout, LAN (30 mg) was administered im at 10-14-day intervals. Time intervals between injections were then individually tailored to normalize IGF-I levels. LAN was administered for 12 (6-36) [median (range)] months. GH and IGF-I levels decreased from 13 (7-20) [median (interquartile)] microg/l to 3.2 (1.7-6.2) microg/l (p<0.0001) and from 780 (596-1000) microg/l to 264 (180-530) microg/l (p<0.000001), respectively. Seven patients were resistant to treatment. Among the 50 sensitive patients, GH levels fell below 2.5 microg/l in 52% (and below 1 microg/l in 18%), IGF-I levels normalized in 72% and both results were obtained in 46%. IGF-I values normalized in 87% of patients treated every 14 days, in 100% every 21-28 days, in 69% every 10 days and in 22% every 7 days. No different control of GH/IGF-I hypersecretion was evidenced between patients previously treated or not by Tx and/or Rx. Patients with the lowest basal hormonal levels and those over 55 years showed greater responsiveness (both p<0.05). The maintenance of LAN schedule up to 18 months determined a further suppression (p=0.04 for IGF-I). A reduction of tumor size was shown in 60% of evaluated patients (6/10). HbA1c slightly increased in 42% of patients and gallstones were observed in 16%. LAN is a very effective tool in the treatment of acromegaly: its chronic administration normalizes GH/IGF-I levels in most patients, shrinks the tumor in a high percentage of patients and seems to control hormonal hypersecretion as primary treatment as well as neurosurgery.