Food-borne benzo[a]pyrene (B[a]P) was administered daily to juvenile grouper (Epinephelus areolatus) at two environmentally realistic concentrations (a low dose of 0.25 microg B[a]P/g body wt/d and a high dose of 12.5 microg B[a]P/g body wt/d) to investigate and relate temporal changes in body burden of B[a]P, hepatic ethoxyresorufin-O-deethylase (EROD) activities, growth, RNA:DNA ratio, estradiol, testosterone, and triiodothyronine (T3). After feeding with B[a]P diets for four weeks, fish were fed with normal diet for another four weeks to study recovery of the various biomarkers during the depuration period. After one week of exposure, both body muscle B[a]P burdens and hepatic EROD activities significantly increased. Body burdens were stable in tissues until the fourth week of exposure, when concentrations in the high-dose group increased markedly, at which time a concomitant decrease in EROD was found. During the depuration period, body burdens decreased in the second week, and EROD declined in the first week. Growth and RNA:DNA ratio were unaltered. Despite large variations found in sex steroid levels, elevation of testosterone was clearly evident in the fourth week, showing that B[a]P may disrupt the balance of sex steroids in fish. Significantly, increases in plasma-free T3 concentrations were found in the fourth week of exposure and the first week of depuration, suggesting that development and reproduction may potentially be at risk during chronic exposures. Our data also suggest that these hormonal disturbances are not persistent and that normal hormonal levels can be restored soon after contamination is abated.