We investigated the influence of packaging materials with high, medium and low oxygen transmission rates (OTR) on the development of 2-thiobarbituric acid-reactive substances (TBARS) and astaxanthin retention in rainbow trout fillets. Three different levels of astaxanthin, during dark or illuminated frozen storage were studied. Samples were analyzed after 17,29 and 36 wk frozen storage. Rancidity developed more rapidly in packages with high OTR. This effect was more pronounced in illuminated samples, also verified by sensory evaluation. Fillets with highest astaxanthin content reached maximum TBARS after 29 wk. The two less pigmented sample groups reached maximum after 17 wk frozen storage, indicating antioxidative effects of astaxanthin.