Objectives: This study aimed to determine the effectiveness of sildenafil citrate on the erectile dysfunction of and satisfaction on sexual performance of married male Filipinos 30-50 years old. It likewise aimed to determine the effect of sildenafil citrate on the onset of erection, ejaculation latency period, detumescence time, refractory period, grade on penile erection and finally on the patient and wife's overall treatment satisfaction. Methods: The study is a placebo, double-blind, crossover clinical study to determine the effectiveness of sildenafil citrate on erectile dysfunction and satisfaction on sex\jal performance among mid-adult married, male, Filipinos conducted in July to October 2006 and included healthy, married, male Filipinos working in or near a tertiary hospital and those seen at OPD Urology Clinic who fall under the age of 30 to 50 years. A sildenafil citrate or matching placebo dose was 50 mg. Effectiveness was assessed by the scores of IIEF-5, mean scores of minutes of onset of erection, ejaculation latency period, detumescence time and penile hardness. Results: Patients upon taking sildenafil, had shorter latency period, duration of erection and detumescence in both first and second occurrences than when they took the placebo. The mean grade of penile hardness is significantly higher when taken the sildenafil (3.5) compared to when they took the placebo (2.9) (p