In a randomized, placebo-controlled, crossover study, 15 ambulatory pa tients with Raynaud's phenomenon, treated for three weeks with ketanserin 80 mg/day and pentoxiphylline 1,200 mg/day, were evaluated by subjective symp tom scores, daily frequency and duration of attacks, and photoplethysmog raphy, at room temperature and after cold test. Reduced subjective symptoms and duration of attacks, together with improved cold test plethysmography, were significant only after ketanserin. All subjective symptom scores also im proved after ketanserin but only for cyanosis and paresthesia after pentoxiphyl line. Excellent results were obtained in 4 cases after ketanserin and in 1 case with pentoxiphylline. The authors discuss the greater importance of antivaso spastic action over antiaggregating and hemorheologic effects in Raynaud's phenomenon therapy, as well as the pathogenetic role of serotonin.