To compare the efficacy of apomorphine and sildenafil in men with nonarteriogenic erectile dysfunction (ED), 40 men were studied. Post-injection penile peak systolic velocity was greater than 25 cm s(-1). Twenty men started on apomorphine 2 mg and 20 on sildenafil 50 mg, the doses titrated up to 3 and 100 mg, respectively, if necessary. After a 1-week washout period each group switched to the other treatment mode. Efficacy was the percentage of attempts resulting in erections firm enough for intercourse, based on an event log data. The majority (85%) of the men had concomitant diseases, risk factors for ED and 95% were heavy smokers. The overall success rate of apomorphine was 62.7%, compared with 73.1% of sildenafil (Yates-corrected chi-square, P < 0.0004). The response to apomorphine 2 mg and sildenafil 50 mg was age related. Sildenafil was statistically more effective than apomorphine in impotent men with normal penile Doppler. Given the contraindication of sildenafil in men taking nitrates and the quick time of action of apomorphine, the two drugs are satisfactory first line therapeutic tools in such individuals and the choice should be based on patient's needs and preferences.