Objective: TO evaluate the efficacy of the phosphodiesterase type 5 (PDE5) inhibitors in the treatment of Raynaud's phenomenon. Data Sources: Searches of MEDLINE (1966–March 2006) and Web of Science (1980–March 2006) were conducted; search terms were sildenafil, tadalafil, vardenafil, phosphodiesterase, and Raynaud. Studies and case reports published in English were retrieved. Additional references were identified in bibliographic reviews. Data Synthesis: Several small studies and a number of case reports have described the use of PDE5 inhibitors in patients with either primary or secondary Raynaud's phenomenon. The data from the best designed study show a reduced attack frequency and duration, reduced Raynaud Condition Score, and increased capillary blood flow in patients with secondary Raynaud's phenomenon. Conclusions: Available evidence suggests that sildenafil may be associated with improved microcirculation, symptomatic relief, and ulcer healing in patients with secondary Raynaud's phenomenon. Limited information suggests similar effects with tadalafil and vardenafil. Improved blood flow and clinical improvements have also been observed in some patients with primary Raynaud's phenomenon treated with PDE5 inhibitors; however, studies have yielded conflicting results.