The objective of this study was to evaluate the importance of Doppler ultrasonography in diagnosing renal artery stenosis in transplanted kidneys using angiography as the accepted gold standard. Fourteen kidney graft recipients with clinical severe hypertension, impaired renal function, or both had their renal artery blood flow studied by Doppler ultrasonography before angiography. Seven patients had renal artery stenosis diagnosed by angiography. In six of them, the same diagnosis was achieved by Doppler ultrasonography, and in one patient, Doppler ultrasonography and angiography showed total occlusion of the renal artery. In six patients, both exams were normal. The only false-negative result was in an 8-year-old patient whose graft was placed in the left flank. The Doppler ultrasonography specificity was 100% and its sensitivity was 87.5%. The predictive value of a positive test was 100%; the predictive value of a negative test was 85.7%. Doppler ultrasonography of the renal artery in transplanted kidneys showed an accuracy of 92.86% in diagnosing renal artery stenosis. Because the technique is noninvasive, it should be considered as a first-line screening test.