Background: No medical therapy has been shown to reduce the rate of restenosis following percutaneous transluminal coronary angioplasty. We examined the existing evidence for the use of omega-3 fatty acids in this capacity with the tool of meta-analysis. Methods: A computerized search and a bibliographic review of published articles were performed. Abstracts were identified through journals, Index Medicus, and an unpublished listing of recent requests for fish oil for experimental use. All English-language randomized clinical trials with available reports were included in the analysis. The quality, design differences, and outcomes were evaluated for each study. Results: For four studies that used angiography to define coronary restenosis, the absolute difference in restenosis rates between treatment and control groups was 13.9% (95% confidence interval [CI], 3.2% to 24.5%). Furthermore, regression analysis revealed a positive linear relationship between the dose of omega-3 fatty acids used and the absolute difference in restenosis rates (r=.99, P<.03). When three studies that used stress testing as a means of determining restenosis rates were added to the four studies that used angiography, the risk difference was 5.1% (95% CI, —3.8% to 13.9%). Conclusions: Restenosis after coronary angioplasty is reduced by supplemental fish oils, and the extent of the observed benefit may be dependent on the dose of omega-3 fatty acids used. © 1993, American Medical Association. All rights reserved.