According to foreign data somatotropinoma volume reduction was noted more than at a half of the patients receiving somatostatin analogs within 12 months as the first line of acromegaly treatment, however there is no data about tumor-supp ressive effect of Octreotid-depot. We assessed somatotropinoma volume during Octreotid-depot treatment in patients with an active acromegaly, and also tried to indentify possible predictors of tumor volume reduction during somastatin analogs treatment. Open prospective study include 18 patients with acromegaly (16 women, 2 men, age from 22 till 76 years old); after non-radical adenomectomy (n=5) and as first line of treatment (n=13). Patients received Octreotid-depot continuously within 12 months. Brain MRI was carried out before and after 12 months of Octreotid-depot therapy. Change of tumor volume for 20% from initial was interpreted as "significant". The GH level 2,5 ng/ml and the normal IGF-1 level were noted in 7 (38,9%) patients; GH ;2,5 ng/ml either the normal IGF-1 level, or simultaneous decrease in the GH and IGF-1 levels more than 50% from initial - in 8 (44,4%) patients, absence of effect from treatment - in other 3 cases. Significant tumor volume reduction was found in 12 (66,7%) of 18 cases, and degree of reduction varied from 23 to 97% (median 42% [38; 74%]); stabilization of the a tumor volume - in 5 (28%) patients; insignificant change of the sizes of a tumor (-7% and +12,5%) in other 2 patients. It wasn't revealed essential correlations between degree of tumor volume reduction and the GH and IGF-1 levels before and after somatostatin analog treatment, and also initial tumor volume.