PURPOSE: The purpose of this study was to test the hypothesis that with the range gate fixed, random adjustment of the pulse repetition frequency will offer a rapid and accurate way to avoid misinterpretation of range ambiguity. BACKGROUND: Traditionally, to avoid the misdiagnosis of Doppler artifacts caused by range ambiguity, time must be spent on checking the flow patterns in the calculated phantom range gates. METHODS: Twenty-four patients (mean age 64 +/- 15 years, 15 men and nine women) with mitral regurgitation were included in the study. Pulsed Doppler evaluation was performed with sample volume initially at the shallow left ventricle and then, along the direction of ultrasonic beam, at the calculated range gate distal to the mitral valve to search for the high velocity Doppler signal. The highest velocity scale was initially selected. After detection of high velocity signal, the velocity scale was lowered to achieve the lower pulse repetition frequency. RESULTS: For all patients, a high velocity regurgitant Doppler signal could be recorded both distal to the mitral valve and at the shallow left ventricle. Such signal persisted at the range gate distal to the mitral valve but disappeared at the range gate at the shallow left ventricle after manual adjustment of the velocity scale. The sensitivity, specificity, and accuracy of disappearance of the high velocity Doppler signal after adjustment of the pulse repetition frequency for confirmation of a phantom phenomenon are 100%, 100%, and 100%, respectively. CONCLUSIONS: Without the necessity of exact information about the pulse repetition frequency used, random adjustment of the pulse repetition frequency for the selected gate range is a rapid and exact method for initial differentiation of in situ from phantom signal in pulsed Doppler echocardiography.