BACKGROUND AND AIM: The marine long-chained n-3 polyunsaturated fatty acids seem to have antiarrhythmic effects in humans. Similar effect has also been postulated for alpha-linolenic acid, a plant-derived polyunsaturated fatty acid--from the n-3 family. The purpose of the study was to examine the relation between the content of alpha-linolenic acid in cell membranes and the risk of malignant arrhythmias as assessed by determination of heart rate variability (HRV). METHODS AND RESULTS: Patients at high risk of sudden cardiac death (52 with a previous myocardial infarction and 29 with chronic renal failure on dialysis) were enrolled as well as 64 healthy volunteers. The cell membrane content of alpha-linolenic acid was analyzed by gas chromatography and related to 24-hour HRV, which was measured in all subjects. No correlations were found between levels of alpha-linolenic acid and 24-hour HRV. CONCLUSION: The present study was unable to demonstrate a positive correlation between cell membrane levels of alpha-linolenic acid and HRV. Our results suggest that alpha-linolenic acid per se is devoid of an antiarrhythmic effect, though this effect could arise from its conversion to the longer chained n-3 PUFA, usually derived from fish.