Hemorheological changes were more recently believed to be responsible for the pathogenesis of the Raynaud's phenomenon. In order to verify such changes, the authors report the data on red blood cell deformability obtained from a study performed in 8 patients with cold-induced Raynaud's phenomenon. From the evaluation of these data it seems likely that hemorheological changes observed during the phenomenon are the consequence of the ischemia and not vice versa.