Background: Clomiphene citrate (CC) is the first line agent used for ovulation induction in patients with polycystic ovarian syndrome (PCOS). However, there is marked discrepancy between the ovulation and pregnancy rates achieved, which may be attributed to the undesirable effect of CC on cervical mucus and endometrium. Objective: The aim of this study was to evaluate the effect of Isosorbid monoitrate (ISMN) as nitric oxide (NO) donors on the ovulation and pregnancy rates in an ovulatory women with PCOS treated with CC. Materials and Methods: Ninety patients with PCOS were randomly allocated into three groups. Patients in group A) were treated with 100 mg CC for five days starting from the fifth day of the cycle. Patients in group B) and C) received 10 mg and 20 mg of ISMN respectively in addition to CC, applied vaginally till the diagnosis of ovulation. Results: There was a significant increase in the ovulation and pregnancy rates in the patients treated with CC+ISMN as compared with patients treated with CC alone (p< 0.001). Conclusion: Concomitant use of NO with CC seems to improve the ovulation and pregnancy rates in the patients with PCOS with no significant increase in side effects as compared with CC alone.