ETHNOPHARMACOLOGICAL RELEVANCE: Herba of Epimedium koreanum is used in traditional Chinese and Korean herbal medicine as a potent enhancer of erectile function. Icariin, the main active component of Epimedium koreanum, possesses many biological effects, such as improving cardiovascular function, hormone regulation, immunological function modulation, and anti-tumor activity. AIM OF THE STUDY: This study supports the traditional use of extracts from Epimedium species in erectile dysfunction. MATERIALS AND METHODS: The Epimedium koreanum dry extract was suspended in wheat germ oil using lecithin and bee wax for oral administration. The effect of oral administration of two compositions (E-01 and E-02) standardized by their icariin content on the number of complete intromissions, the number of ejaculations, and the latent period of ejaculation (LPE) in rats were evaluated. E-01 and E-02 were administered orally for 10 days to the experimental animals. The control animals received olive oil for 10 days. On day 10, 0.5h after the dose was administered to male rats, one virgin female rat was placed with one male rat. RESULTS: The number of complete intromissions increased to 23.3+/-2.6 in the E-01 and E-02 group (dose 300 mg/kg body weight) (b.wt) and to 20.1+/-2.3 in the E-02 group (dose 750 mg/kg b.wt) compared with 15.2+/-2.4 in the control group of aged rats. The number of ejaculations increased from 1.1+/-0.3 in the control-aged group to 2.6+/-0.4 in the E-01 group. The LPE of male rats was 14.2+/-1.8 min in the control-aged group. The LPE of the aged group was reduced to 9.8+/-1.5 min, 9.8+/-1.6 min, and 11.4+/-1.8 min when treated with E-01 at a dose of 300 mg/kg b.wt, and E-02 at a dose of 300 mg/kg b.wt and 750 mg/kg b.wt, respectively. CONCLUSION: It was established that oral administration of lipid-based suspension of dry extract of Epimedium koreanum in wheat germ oil improved erectile function of aged rats.