Objective: A systematic review of the literature was conducted relating to the continuation of warfarin therapy at the time of coronary angiography, with or without percutaneous coronary intervention, to determine the bleeding risk of these patients. Methods: A search of a major electronic database was independently conducted by two reviewers from 1960 to December 2009. Studies were included if they met the following criteria: were original; included patients who were undergoing coronary angiography/catheterization with or without angioplasty/stent placement and were receiving uninterrupted warfarin therapy throughout the periprocedural period; and reported the number of bleeding events and procedure related complications. Based on the inclusion and exclusion criteria, a total of eight studies (one randomized, four cohort and three case series) were included for analysis. Results: The pooled odds ratio (95% CI) for procedure-related complications in continued warfarin versus nonanticoagulated patients, in those studies that had comparison groups, was 0.53 (0.29-0.94) and for combined major bleeding and procedure-related complication was 1.01 (0.29-3.51). However, there was significant heterogeneity (p = 0.001; I2 = 81%) in retrospective studies and no heterogeneity in prospective studies (I2 = 25%). The pooled incidence (95% CI) of major bleeding and periprocedural complications for all studies, including case series, was 0.037 (0.024-0.057). There was no significant heterogeneity (p = 0.32; I2 = 14.1%). Discussion: Continuing warfarin therapy during coronary angiography and percutaneous intervention appears to be safe, with no increased incidence of major bleeding and periprocedural complications. However, the quality of evidence is low due to several limitations of a number of the studies included in our article. A multicenter randomized trial is necessary to determine the optimal periprocedral strategy for patients receiving uninterrupted warfarin therapy undergoing coronary angiography and percutaneous coronary intervention.