Diets rich in lycopene from tomato products as well as greater concentrations of blood lycopene have been associated with a decreased risk for prostate cancer in epidemiologic studies. However, little is known about factors modulating lycopene absorption, metabolism and tissue distribution in humans and animal models of prostate cancer. A 2 x 4 factorial design was used to measure the effects of androgen status (castrated vs. intact), dietary lycopene concentration (0.00-5.00 g/kg lycopene) and their interaction on tissue lycopene accumulation and isomer patterns in male F344 rats. Male F344 rats ( 14 wk old; 44 castrated, 44 intact) were randomly assigned to one of four diets containing total lycopene concentrations of 0.00, 0.05, 0.50 or 5.00 g/kg as beadlets and fed for 8 wk. Tissue total lycopene and cis/trans lycopene profiles were determined by HPLC. Tissue and serum lycopene concentrations increased significantly (P < 0.01) as dietary lycopene levels increased between 0.00 and 0.50 g/kg. No further increases in serum or tissue concentrations were seen in rats fed dietary lycopene between 0.50 and 5.00 g/kg. As dietary lycopene increased, so did the percentage of cis lycopene in the liver (P < 0.05), due primarily to an increase in the 5-cis isomer. Castrated rats accumulated twice (P < 0.01) the liver lycopene as compared to intact controls, with no effect of castration on serum lycopene or adrenal, kidney, adipose, or lung tissue concentration. Livers from castrated rats had a greater proportion of cis-lycopene than those of intact rats (P < 0.05). A significant interaction between dietary lycopene concentration and androgen status was seen for liver lycopene concentration (P < 0.01). We conclude that serum and tissue lycopene reaches a plateau between 0.05 and 0.50 g/kg dietary lycopene, the tissue cis/trans lycopene ratio increases with greater dietary lycopene and androgens modulate hepatic lycopene metabolism.