The authors have in their care 286 Raynoud syndrome patients. They present their experience in the study of the microcirculation and the treatment of these patients. In 81% (232 patients, 196 women and 36 men) of the cases they did not find any underlying diseases. In the group of the patients with secondary Raynaud's syndrome (35 women and 19 men) underlying diseases, possibly leading to microcirculatory disturbances, could be identified. In the primary Raynaud's syndrome group the main capillary diameter measured by capillary microscopy was 15 +/- 4 micron. In patients with progressive systemic sclerosis the mean diameter was 43 +/- 9 micron. In the group of women with primary Raynaud's syndrome the authors performed laser Doppler measurements of the nailfold microcirculation. During the reactive hyperaemia test basal values (18.2 +/- 6.2 Perfusin Units, P. U.) and reactive hyperaemia values (a mean of 180% growth compared to the basal values) were similar to that perfusion values referred in the literature. In the progressive systemic sclerosis group the basal flow (9.3 +/- 3.3 P. U.) and the reactive hyperaemia (a mean of 20% increase compared to basal values) were significantly lower. Concerning the fact that the progression of Raynaud's syndrome into systemic autoimmune disease--mainly to progressive systemic sclerosis may be predicted, it is important to follow up carefully all patients with Raynaud's syndrome.