PURPOSE: To (a) critically appraise available randomized controlled trials (RCTs) addressing the efficacy of long-chain omega-3 fatty acids as secondary agents for prevention of hypertriglyceridemia and (b) make recommendations for clinical practice. DATA SOURCES: Two independent reviewers examined all RCTs from 1994 to 2003 identified in several databases, extracted data from each study, and used the previously tested Boyack and Lookinland Methodological Quality Index (MQI) to determine study quality. CONCLUSIONS: Ten studies reported long-chain omega-3 fatty acids to be effective in the treatment of hypertriglyceridemia. The average decrease in triglycerides was 29%, total cholesterol 11.6%, very low density lipoprotein (VLDL) 30.2%, and low-density lipoprotein (LDL) 32.5%. One study found LDLs to increase by 25%. The average increase in high-density lipoprotein was 10%. The overall average MQI score was 36% (range = 26% to 54%). Many of the RCTs had serious shortcomings, including short duration, lack of a power analysis, no intention-to-treat analysis, no report of blind assessment of outcome, and lack of dietary control as a confounding variable. IMPLICATIONS FOR PRACTICE: Overall study methodology was weak. Although the evidence supporting use of long-chain omega-3 fatty acids in the secondary prevention of hypertriglyceridemia is reasonably strong, until there are larger RCTs of better methodological quality, it is not recommended that practitioners treat hypertriglyceridemia with omega-3 fatty acid supplementation in lieu of lipid-lowering medications.