PURPOSE: To evaluate perflenapent emulsion as a contrast agent for ultrasound (US) of the liver, kidneys, and vasculature. MATERIALS AND METHODS: A randomized, double-blind, placebo-controlled, multicenter trial of 151 patients was performed. Investigators and blinded readers compared sonograms obtained after intravenous administration of perflenapent emulsion (0.05 mL/kg) and of a placebo with baseline sonograms. RESULTS: Contrast enhancement occurred in 140 of 149 patients (94%) after perflenapent administration and in 12 patients (8%) after placebo administration (P < .001). Enhancement lasted 5.0-15.4 minutes with perflenapent and 0.1-1.7 minutes with the placebo (P < .001). Perflenapent enhanced or facilitated visualization of blood flow, abnormal structures, masses, and lesions in 138 of 147 patients (94%) versus 12 of 147 (8%) for the placebo (P < .001). Improved visualization assisted in the diagnosis in 105 of 143 perflenapent studies (73%) compared with five of 143 placebo studies (3%) (P < .001). Diagnostic information affected case management in 71 of 148 patients (48%) after perflenapent administration and in nine of 148 patients (6%) after placebo administration (P < .001). Adverse effects associated with perflenapent were few and mostly mild, occurred within 30 minutes, and resolved without treatment. CONCLUSION: Perflenapent emulsion is a safe and effective contrast agent for US of the liver, kidneys, and vasculature.