To estimate the prevalence of diabetes mellitus (DM) among the patients with acromegaly residing in the Moscow region (MR). A total of 93 patients aged from 48.0 to 64.5 (mean 57.5) years presenting with acromegaly from 7.5 to 20.25 (mean 13.0) years in duration were available for the examination. Twenty seven of these patients developed diabetes mellitus prior to acromegaly. Oral glucose tolerance test (OGTT) for diagnostics of DM was performed in 66 patients. The overall prevalence of diabetes mellitus among the patients with acromegaly was estimated at 51.6% which is higher than that in the general population of the Moscow region and worldwide (2.3% and 8.3% respectively). The prevalence of DM among women was higher than in men (55.1% and 33.5% respectively; p<0.05). It increased with age (from 14.3% in the patients aged between 36 and 45 years to 48.3% at the age above 56 years) and with duration of acromegaly (from 40.6% in the patients with the duration of the disease up to 8 years to 60.5% in those with acromegaly during more than 15 years; p<0.05). Asymptomatic diabetes was diagnosed in 34.8% of the 69 patients which is also higher than the prevalence of asymptomatic type 2 diabetes mellitus in a random sample from the adult population of MR and in the group with the enhanced risk of DM2. The prevalence of DM among the patients in the controllable and uncontrolled phases of acromegaly was 57.1% and 49.2% respectively (p>0.05). The prevalence of DM2 among the patients with acromegaly is significantly higher than in the world's general population; it depends on the patients' age and sex and as well as on the duration of acromegaly.