Prospective, randomized, double blinded trial. Survivors of VT and VF with an implantable defibrillator were randomized, 100 to dietary supplementation with n-3 polyunsaturated fatty acids(PUFA) or 100 to a placebo. Adherence to the supplement were assessed by measurements of plasma, red cell, and adipose tissue n-3 fatty acid concentrations. The primary outcome variable was the incidence of recurrent VT or VF, but secondary variables were also assessed using serial implantable cardioverter defibrillator (ICD) assessment, correlation of the rhythms with the biochemical measurements of n-3 fatty acids, hospitalization rates and quality of life. The (ICD) was the best protection available to patients and stored rhythm electrograms which allowed documentation of rhythm endpoints.