One hundred consecutive echocardiograms performed on adults using transthoracic and transesophageal (TEE) transducers were analyzed in order to determine the prevalence of spontaneous contrast (SC) and the factors associated with it. Indications for study included complex congenital cardiopathy, evaluation of valve lesions or prosthetic valves, dissecting aortic aneurysm, cardiac masses and evaluation of ventricular function. SC was observed only with TEE and appeared in 25% of cases, most frequently in left atrium. Factors associated with contrast included mitral valve disease and replacement, ventricular dysfunction, left atrial dilatation and atrial fibrillation. An important relationship existed between SC and presence of thrombi. Atrioventricular valvular regurgitation was not associated with SC. Results are compared with those of previous series.