Objective of the study was to evaluate the effect of combination of oral Coenzyme Q10 (CoQ10), with clomiphene citrate (CC) for ovulation induction in CC-resistant polycystic ovary syndrome (PCOS).In a prospective controlled randomized trial performed in a university hospital and private practice setting. One hundred ten infertile women with PCOS resistant to CC were randomized to either combined CC/CoQ10 (51 patients, 82 cycles) or CC 150 mg/day alone (50 patients, 71 cycles) for ovulation induction in patients with CC-resistant PCOS.