Due to the development of the duplex mode, combining ultrasound images with Doppler recording, and especially the development of flow colour coding. Doppler is now increasingly used to investigate the kidney and male genital tract. It is now the technique of choice in the initial diagnosis of certain renal diseases: primary renal vein thrombosis, iatrogenic and malformative arteriovenous anomalies, vascular complications of renal transplantation, and for examination of the scrotal contents in a context of acute scrotum or investigation of the cavernosal arteries in the case of erection disorders. It allows a rapid diagnosis and guides the subsequent radiological assessment. Doppler can also provide useful or even essential additional information in the case of a known abnormality such as renal cancer, in which it defines the venous extension when CT scan is technically insufficient. In certain fields, such as diagnosis of renovascular hypertension or exploration of the prostate, the place of Doppler is still poorly defined and remains controversial, except in a few specialised centres equipped with sophisticated apparatuses used by experienced operators. After briefly reviewing Doppler techniques and the basic steps in interpretation, the authors define the contribution and limitations of colour Doppler in the investigation of the urinary tract and male genital tract. Normal appearances and the results of Doppler-ultrasound in nephrourological disease are illustrated.