['To evaluate prospectively and compare the clinical response and the change in nucleotides correlating with haemodynamic changes in the cavernosal arteries after an intracavernosal injection (ICI) with vasoactive agents with or without oral sildenafil in men with erectile dysfunction (ED).', 'In all, 80 patients with ED were prospectively evaluated by clinical assessments, measuring nucleotides in blood plasma and haemodynamics in cavernosal arteries. All patients had colour Doppler ultrasonography (CDU) twice with an interval of 5 h. First, each patient had CDU after ICI with trimix (0.25 mL) or prostaglandin E1 (PGE1, 5 microg), and the second CDU was after ICI trimix given 1 h after oral placebo (group I), sildenafil 25 mg (group II) or 100 mg (group III) and after ICI with PGE1 at 1 h after oral placebo (group IV) or 100 mg sildenafil (group V). Levels of cGMP and cAMP in peripheral venous and penile cavernosal blood plasma were measured at 15 min after ICI.', 'The mean peak systolic velocity (PSV) at 5, 10, 15 min, and resistive index at 10 min in the second CDU after ICI with trimix, were significantly increased in group III. The mean (sem) levels of cavernosal cGMP were significantly increased in group III and V, from 1130.1 (313.5) to 2056.7 (580.4) and 1017.0 (214.2) to 1905.2 (915.0) fmol/mL, respectively. cAMP was significantly increased in group V, from 9533.1 (2068.4) to 12150 (3684.2) fmol/mL.'] Is why a combined intracavernosal injection with trimix and oral sildenafil reliable therapy in the ultrasonographic evaluation of erectile dysfunction?