SMS 201-995 was administered to 40 acromegalic patients, in a multicentric study. Some of the results have been analyzed from 37 patients who remained under a long term treatment. Clinical improvement was noted in most patients, especially as concerns soft tissue swelling, sweating, headache. Digestive adverse effects were noted, leading to the drop-out from the protocol (in 4 patients) or in most patients to a slight discomfort related to increasing doses. There was an effect for all the doses used (300, 600, 900, 1500 micrograms in 3 subcutaneous injections per day), compared with pretreatment values, if we consider the mean GH value of each cycle obtained under the different dosages. The highest dose was most effective than the lowest in some cases. However in most patients the 300 micrograms dose was efficient. We could not obtain normalization of GH secretion. However 22/37 patients could reach a good score as concerns the number of GH values less than 5 micrograms/l, during circadian evaluations. In 5/37 patients, the antisecretory effect was insufficient (mean GH above 50% of the pretreatment level). Reduction in tumor volume was highly significant (more than 50%) in 2/11 patients. In conclusion, this study shows the efficacy of SMS 201-995 in improving clinical signs and symptoms of acromegaly, and GH hypersecretion in approximately 80% of the patients. General and metabolic tolerance are rather good. Some points concerning tolerance remain to be investigated.