The symptomatic effects of felodipine (Plendil) have been assessed in 10 patients with primary Raynaud's phenomenon in a single blind study. After 2 weeks on placebo, the patients were treated for 6 weeks with felodipine, the dose being titrated stepwise every 2 weeks, starting with 5 mg, and increasing to 10 mg and 20 mg once daily if symptoms persisted. After the drug period the patients received placebo for 2 weeks. Objective measurement by cold exposure finger plethysmography did not show any benefit of felodipine in the higher temperature range, taking 33 degrees C as reference point. However, when using 24 degrees C as the reference point, the area under the plethysmography versus temperature curve (AUC) for 5 mg felodipine were significantly larger than the initial placebo area. The AUC during recovery from cold exposure for the maximal accepted dose of felodipine was significantly larger than for the initial placebo period. Subjective judgement by the patients showed a significant reduction in the number of Raynaud attacks and a trend to a shorter duration of attacks with the maximal dose of felodipine. Two patients became free from attacks of Raynaud's phenomenon. Felodipine 10 mg once daily was well tolerated. It was regarded as the optimal dose to treat patients with Raynaud's symptoms.