Arctic animals utilize periods with high food availability for feeding and lipid deposition, whereas they rely on stored lipids during unfavorable periods. Hence, many arctic inhabitants exhibit profound seasonal cycles of fattening and emaciation. In the Arctic, feeding is associated with fat deposition and contaminant accumulation. When lipids are mobilized, accumulated contaminants are released into the circulation. Consequently, blood contaminant concentrations may increase markedly and result in a redistribution of the contaminant(s) from “insensitive”, adipose tissues to sensitive organs, and increased contaminant bioavailability. Such variations complicate interpretations of pollutant toxicity, both in effect studies and in monitoring programs, and remains an important future reseach area. In the present study, we will use arctic fox (Alopex lagopus) as a model species for investigating tissue distribution and bioavailability of organochlorine contaminants (OCs) in relation to natural variations in lipid status (field study). These data will be supplemented and validated through a contamination study with blue fox (A. lagopus), where the seasonal changes in lipid status of wild fox are simulated in the laboratory. In both the field and laboratory study, possible effects of OCs on steroid hormone synthesis, and plasma levels of hormones, vitamin E and retinol will also be assessed.