Objectives. To evaluate the clinical efficacy and the effects on the quality of life of iloprost, a prostacyclin analogue, used according to a new protocol in patients with Raynaud's phenomenon secondary to systemic sclerosis. Methods. In this randomized study, we treated 30 patients with iloprost, given by intravenous infusion, at progressively increasing doses (from 0.5 to 2 ng/kg/min) over a period of 6 h each day for 10 days in two consecutive weeks, with repeated cycles at regular intervals of 3 months for 18 months. The results were compared with those obtained in 30 other patients who received the same drug but with different dosing schemes. Results. The total average daily duration of the attacks, the average duration of a single attack and the average daily frequency of the attacks were reduced significantly in all treatment groups, but the comparison between the groups demonstrated significant differences between patients treated with the new protocol and the others at later times (12 and 18 months). The effects on the quality of life in the group treated with the new protocol, evaluated with the Short Form-36, demonstrated a marked improvement regarding both the scale relating to the physical aspect of the illness and, especially, the scale relating to the mental aspect. Conclusions. In patients with systemic sclerosis, cyclic intravenous iloprost infusion is efficacious in the treatment of Raynaud's phenomenon. The protocol that we used, compared with others, not only has favourable clinical effects but also leads to a marked improvement in the quality of life.