The highly complex embryological development of the left renal vein compared to its right counterpart results in greater variations which are clinically significant. The study aimed to identify these variations and to document its incidence. Cadaveric study: 153 kidney pairs were harvested en bloc, dissected, 100 resin casts prepared and 53 plastinated; renal venography performed on further 58 adults and 20 foetal cadavers. Clinical study: (retrospective analysis): a) radiological study, 104 renal venograms; b) live related renal transplantation, 148 donor left kidneys; c) abdominal aortic aneurysm surgery, 525 patients. Total sample size: 1008. Renal collars observed in 0.3%; retro-aortic vein 0.5%; additional veins 0.4%; posterior primary tributary 23.2%, (16.7% Type IB; 6.5% Type IIB, cadaveric series, only). Our results differ significantly in incidence to that reported in the literature: renal collar 0.2-30%; retro-aortic vein 0.8-7.1%; additional renal vein 0.8-6%. Variations are clinically silent and remain unnoticed until discovered during venography, operation or autopsy. To a transplant surgeon, morphology acquires special significance, since variations influence technical feasibility of operation. Prior knowledge of circum-aortic vein is important when blood samples from suprarenal or renal veins are collected. Collar may provide developed collateral pathway immediately after surgery if renal interruption planned without awareness of its presence. Variations restrict availability of vein for mobilisation procedures. In aortic aneurysm repair, retro-aortic vein is important. During retroperitoneal surgery, the surgeon may visualise a pre-aortic vein but be unaware of an additional retroaortic component or a posterior primary tributary, and may avulse it while mobilising the kidney or clamping the aorta.