The new ultrasound contrast agent Sonazoid was injected in 5 healthy dogs, and the time course enhancement in liver parenchyma, portal vein, spleen, and renal cortex was evaluated. In liver parenchyma and spleen, sustained enhancement was observed from at least 8 to 15 min after injection with the peak at 45 sec (liver) and 20 sec (spleen), whereas in the portal vein and renal cortex, the time course enhancement dramatically decreased after the peak enhancement at 30 sec and 20 sec, respectively. No adverse effect was observed after Sonazoid injection in all the dogs that we examined. Contrast enhanced ultrasound using Sonazoid is believed to be useful for observing the parenchyma of canine liver and spleen.