The system of insulin-like growth factor-I (IGF-I) and its binding proteins is thought to be involved in the pathogenesis of vascular damage under different pathological circumstances. The results of various studies are rather controversial. This study considers the relationship between the activity of this system and the function of microcirculation in acromegalic patients. Thirteen patients with hormonally active acromegaly and 15 healthy controls were included in the study. The growth hormone, free IGF-I, IGF-I, IGF binding protein (IGFBP) -1, -2, -3 and -6 serum levels and parameters of lipid metabolism were determined. The function of microcirculation was determined by laser Doppler fluxmetry and the intima media thickness of the common carotid artery was measured by ultrasound. We noted significant reduction in postocclusive reactive hyperaemia (PORH(max)) (P < 0.01), in thermal hyperaemia (TH(max)) (P < 0.05) and in the velocity of reaction in both tests in the group of acromegalic patients. A significant negative correlation between free IGF-I serum levels and maximal perfusion during thermal hyperaemia TH(max) (P < 0.02) was found in the control group. Statistically significant positive correlation between free IGF-I serum levels and the time to maximal perfusion in postocclusive reactive hyperaemia PORH(max) (P < 0.05) was found in the group with hormonally active acromegaly. Moreover, a positive relationship between IGFBP-1 serum levels and serum levels of total (P < 0.01) and low density lipoprotein (LDL) (P < 0.05) cholesterol was found in the group of patients with acromegaly. We conclude that the function of microcirculation is impaired in patients with acromegaly and that free IGF-I serum levels may affect the microvascular function as measured by laser Doppler fluxmetry. In addition, we found a significant relationship between the serum levels of IGFBP-1 and those of total and LDL cholesterol in the group of patients with hormonally active acromegaly.