The oxidation state of traditional fish products was measured by determining the malondialdehyde (MDA) level by HPLC and the results were compared to those given by a spectrophotometric method. The procedure involves oxidation of the products by incubation at 40 degrees C for 3 d. Samples were steam distilled in a Kjeldahl distillation apparatus and the MDA was determined in the aqueous distillates by HPLC, using a micro-Bondapak C18 column, with mixed mobile phase of 1% acetic acid-acetonitrile (85 + 15; v/v). A total time of 2 min was necessary to assay each distillate and only MDA was detected. MDA can be determined at a level of 1.5 x 10(-8) mol l-1. The highest rate of oxidation of the samples, as shown by the changes in the TBA test and MDA concentration determined by HPLC, was observed in smoked fish and the lowest in dried-salted fish.