The effects of two different vasodilating agents (MgSO4 infusion and the calcium antagonist nifedipine) on circulating levels of calcitonin gene-related peptide (CGRP) were studied in 12 women with pronounced primary Raynaud's phenomenon (PRP) and in 12 healthy females. There were no significant differences with regard to basal levels of circulating CGRP between women with PRP and the control group; median 15.5 (range 10-48) vs. 14 (range 10-69) pmol l-1, respectively. However, treatment with MgSO4 infusion significantly decreased circulating CGRP in women with PRP only from median 15.5 (range 10-48) to 10 (range 10-110) pmol l-1) (P < 0.05). On the other hand 14 days of treatment with nifedipine did not affect circulating CGRP in either of the investigated groups. Erythrocyte magnesium (ery-Mg) levels increased significantly after MgSO4 infusion in women with PRP (2.43 +/- 0.13 vs. 2.52 +/- 0.15 mmol l-1, P < 0.05) but not in the controls (2.51 +/- 0.24 vs. 2.57 +/- 0.28 mmol l-1, ns). In conclusion, the decrease of circulating CGRP after MgSO4 infusion in women with PRP provides further evidence that magnesium plays a significant role in the pathophysiology of PRP.