In this project, two large intervention studies on the effects of n-3 fatty acids from fish in capsules are performed on arrhythmia. Furthermore the project includes an intervention study on the bioconversion of alpha-linolenic acid to EPA and DHA and an experimental study in isolated pig hearts on the effect of n-3 fatty acids on electrophysiology. In the first intervention trial no significant effects of n-3 fatty acids could be detected in patients with arrhythmia, neither on spontaneous PVC’s (premature ventricular contractions), nor on changes in the ECG, which could imply that these markers are not sufficiently sensitive or specific to detect the beneficial effects of fish oil on the heart. The second (multi centre) intervention trial is ongoing. 512 patients with an implanted defibrillator were included in the study. The intervention will continue until January 2005 and results are expected in September 2005. The other planned trials are ongoing.