Abstract The study aims to evaluate short-term teleost hepatocyte cultures to establish dose–response curves for CYP1A induction and to rank the relative potencies of xenobiotics. Hepatocytes isolated from rainbow trout ( Oncorhynchus mykiss) were incubated in vitro in coculture with RTG-2 cells in serum-free, chemically defined medium. Concentration-dependent induction of cytochrome P4501A was observed after treatment of the hepatocytes for 48 h with one of the four polyaromatic hydrocarbons: 3-methylcholanthrene, benzo[ a]pyrene, benz[ a]anthracene, and β-naphthoflavone. The induction response was assessed by measuring 7-ethoxyresorufin- O-deethylase (EROD) and 7-ethoxycoumarin- O-deethylase (ECOD). From the data, EC 50 and maximal induction response values were calculated. The rank order of EC 50 values differed among the four model compounds, depending on the endpoint parameter. EC 50 values for EROD and ECOD also differed in comparison to published affinity data for mammalian arylhydrocarbon receptor. The results of this study indicate the potential of primary teleostean hepatocyte cultures for studies on induction potency and regulation of piscine cytochrome P4501A. A drawback, however, appears to be the pronounced interindividual variation of the quantitative response of the cells.