In neonates, thrombosis beginning in small renal veins and progressing to larger veins is best termed renal venous thrombosis (RVT) since the renal vein is not usually concerned. RVT occurs dominantly in the new-born and affects males more often than females (2:1). Hyperosmolality, maternal prediabetes and angiocardiography contribute to the occurrence or RVT. Early signs and symptoms are largely non-specific with the most reliable being the presence of haematuria (49%) or a palpably enlarged and hard kidney (60%). A falling platelet count, raised FDP level of falling plasminogen level support the diagnosis in 90% of cases. Radiology and nephrosonography are very useful in establishing the presence or absence and functional state of the kidneys. Therapy consists of the maintenance of homeostasis, minimization of spread, correction of uraemia and prevention of renal hypertension from a contracted functionless kidney by elective nephrectomy after 4--6 months. Heparin therapy and peritoneal dialysis have greatly improved the outlook in bilateral cases.