The effects of 17 beta-estradiol (E(2)) and testosterone (T) singly and in combination were tested on juvenile chub (Leuciscus cephalus L.). Vitellogenin (VTG) and 11-ketotestosterone (11-KT) were determined by ELISA in whole body homogenates and the gonads were examined histologically. Testosterone and estradiol, in combination, significantly increased whole body VTG (p < 0.01), but not 11-KT, compared to controls and the T treated groups. The only intersex observed (1/80) was in the combined treatment group. We suggest that VTG measured in whole body homogenates could be used to determine the effects of exogenous steroids in juvenile chub.