Twelve active acromegalic patients (10 women, 2 men) were chronically treated with a long-acting microcapsulated preparation of octreotide (Sandostatin LAR, Novartis). In each case, a growth hormone-producing pituitary adenoma was responsible for the development of acromegaly (microadenomas in 3 and macroadenomas in the rest of the patients). Treatment with long-acting octreotide was indicated for those patients who had not reacted satisfactorily upon previous therapeutic procedures or proved to be unsuitable for irradiation therapy and/or surgery or refused both of these therapies. The preparation was given intramuscularly in every fourth week, generally in a dose of 20-30 mg. After a 6-month treatment, the daily mean of serum growth hormone became suppressed below 2.5 ng/ml in 58.3% of the patients, whereas the growth hormone nadir during oral glucose tolerance test was found at or below 2.5 ng/ml in an even higher proportion of patients (70%). During a 2-year period, the growth hormone-suppressive effect of long-acting octreotide remained stable in all but one patient. The size of the pituitary adenomas remarkably decreased in 50% of this patient cohort. The medication with this preparation was well tolerated. As adverse events, asymptomatic cholelithiasis was detected in 2 patients and biliary sludge-formation in 1 patient. The total number of patients with glucose metabolism disturbances increased only moderately, however, the occurrence of manifest diabetes mellitus became doubled. On the basis of relevant literature data, it can be stated that the mortality rate of successfully treated acromegalics significantly improves. The present retrospective study yields evidence for the microcapsulated octreotide to be an effective tool in the modern therapy of acromegaly.