Purpose: To determine the efficacy of $Carnitil^{(R)}$ (acetylcarnitine, Hanmi, Korea) therapy in idiopathic oligoasthenospermic men. Materials and Methods: Forty-four subfertile men with abnormal semen parameters were treated between March, 2003 and March, 2004 with 3 g of $Carnitil^{(R)}$ daily for 3 months. Changes in semen parameters were evaluated 3 months after this therapy. Results: The mean age was 34.2 years and the mean follow-up duration was 3.7 months. In asthenospemic patients (n=28), semen analysis before and after $Carnitil^{(R)}$ treatment showed an increase in volume ($2.64{pm}1.65;ml$ vs. $3.10{pm}1.60;ml$), motility ($35.1{pm}17.7%$ vs. $45.9{pm}20.4%$) and viability ($51.4{pm}20.3%$ vs. $59.3{pm}13.6%$) respectively. In oligoasthenospermic patients (n=16), semen analysis before and after $Carnitil^{(R)}$ treatment showed an increase in sperm count ($10.7{pm}54.4;million/ml$ vs. $38.4{pm}32.5;million/ml$) respectively. Conclusions: These results suggested that in idiopathic oligoasthenospermic men the empirical medical therapy with acetylcarnitine may be considered as primary treatment.