Cicaprost is a new synthetic prostacylin analogue which is metabolically stable and bioavailable after oral administration; in previous studies it has been shown to have vasodilator antiplatelet effects. In this pilot study, we investigated the clinical efficacy of and patient tolerance to two dosage levels of cicaprost (2.5 micrograms tds and 5 micrograms tds) in the treatment of Raynaud's phenomenon secondary to systemic sclerosis (SSc). This was a three centre, double-blind, placebo controlled study of 49 patients carried out over four winter months. For a period of 10 days, 16 patients were given a placebo, 16 received cicaprost 2.5 micrograms tds and 17 received cicaprost 5 micrograms tds. Response was assessed based on the total number and duration of Raynaud's attacks, the average severity of the attacks, the number of painful attacks as a proportion of all attacks, a digital ulcer count, and the patients' opinion of the treatment. Although the clinical and laboratory parameters of digital vasospasm did not show statistically significant improvement in those who received cicaprost compared with those on the placebo, the severity of attacks lessened in the patients who received cicaprost 5 micrograms tds, and a statistically significant difference was seen in the average severity at week 2 post-treatment (p = 0.02). The apparent lack of overall significance was probably related to the short treatment period and relatively low doses of cicaprost used in this exploratory study. Longer studies with dose titration are probably needed to demonstrate the beneficial effects, if any, of cicaprost in patients with Raynaud's secondary to SSc, and these are being planned.