The aim of the present study was to determine the relevance of serum nitric oxide levels and the efficacy of selective serotonin reuptake inhibitors (SSRI) treatment on premature ejaculation. Sixty married men (aged 20-50) with lifelong premature ejaculation and forty healthy men (aged 24-48) as control group were included in this study. The patients were evaluated by intravaginal ejaculation latency time (IELT) for premature ejaculation (PE). IELT<1 min is accepted PE. Patients with diabetes mellitus, chronic disorders or erectile dysfunction and heavy smokers were excluded. All patients were evaluated with history, physical examination, International Index of Erectile Dysfunction-5 (IIEF-5) score and IELT by stopwatch method. Nitric oxide levels were measured by Griess reaction, and all samples were frozen at -80 degrees C. Patients were randomly categorised 4 group to receive fluoxetine 20 mg day(-1) (Group 1), paroxetine 20 mg day(-1) (Group 2), sertraline 50 mg day(-1) (Group 3) and healthy control (Group 4) for 4 weeks. Baseline and post-treatment findings were compared between the four groups. At the end of 4 weeks, in fluoxetine, paroxetine, sertraline groups mean IELT values showed a statistically significant improvement from the baseline values (P < 0.001, P < 0.001, P = 0.03; respectively). Baseline and 1st month follow-up mean IIEF scores were 24.5 and 23.05, 24.70 and 23.60 (P < 0.05) in group 1 and group 3 respectively; also 23.09 and 23.32 (P > 0.05) in group 2. Baseline serum NO levels were 31.8, 30.44, 30.8 and 42.84 in fluoxetine, paroxetine, sertraline and healthy control groups respectively. NO levels were statistically lower in patients with PE. After treatment of fluoxetine, paroxetine and sertraline, NO levels were increased baseline (35.8, 36.4, 38.08) (P < 0.05). Our findings indicated that PE is associated with decreased serum NO levels. After the SSRI treatment increased, NO may retard ejaculation presumably by central peripheral mechanism. Further studies are needed to confirm this suggestion and the role of NO in pathophysiology and treatment for premature ejaculation.