Fillets of herring (Clupea harengus) were kept in ice for 0, 3, 6 and 9 days prior to storage at -18 °C for 0, 3, 6, 9 and 12 weeks. At each storage point, peroxide value (PV), absorbance at 268 nm (A268), fluorescent products (FP), ?-tocopherol, glutathione peroxidase (GSH-px) and ascorbic acid were measured. As shown by regression analyses, samples held for 6 days on ice formed oxidation products with the highest rate during frozen storage, followed by, for PV and FP, the 9-day samples. These data indicate that severe changes negatively affecting the oxidation process took place in the herring muscle between 3 and 6 days after catch. The rate of antioxidant loss at -18 °C decreased with increased pre-freezing holding, something which was most obvious for GSH-px and ascorbic acid. ?-Tocopherol showed the largest losses, and after 82 days at -18 °C, the 6-day sample had completely run out of this compound. Partial least square regression (PLS) analysis of all data showed that the ice storage had a larger effect than the frozen storage on changes in PV, A268, FP, ?-tocopherol and ascorbic acid. For GSH-px, the relation was the inverse.