Aim: To investigate whether oral treatment with D-004, a lipid extract of the Cuban royal palm fruit, produces antioxidant effects in the prostate tissue of normal and testosterone (T)-treated rats. Methods: In our first experiment, normal rats were distributed into five groups: one group treated with the vehicle and four groups treated with D-004 (100, 200, 400 or 800 mg/kg). In our second experiment, rats were randomized into five groups: a negative control group and four T-injected groups. The latter were comprised of a positive control group treated with the vehicle, and three groups treated with D-004 (200, 400 or 800 mg/kg). Results: In normal rats, D-004 (100-800 mg/kg) inhib- ited significantly and dose-dependently iron-initiated malondialdehyde (MDA) accumulation in prostate homogenates (35.7%-80.0%) vs. the controls. D-004 (200-800 mg/kg) significantly reduced baseline MDA and carbonyl groups in prostate homogenates of normal rats to approximately 80% and 50%, respectively, and totally (100%) in T-treated rats. Conclusion: Oral treatment with D-004 reduced MDA and carbonyl groups dose-dependently and markedly in normal and T-injected rats. These findings show that D-004 given at doses effective to prevent prostate hyperplasia also produces antioxidant effects in the prostate tissue. (Asian J Andrl 2008 Jul; 10: 659-666)