The veins of the popliteal fossa are more complex than is generally realised. It is frequently taught that the short saphenous vein need only be divided deep to the popliteal fascia. However, the pattern and level of termination of the short saphenous vein shows wide variation. Sometimes, the short saphenous vein is normal and the pathology involves other veins. The 'vein of the popliteal fossa' may sometimes be present as a large tortuous varicosity and pierce the fascia to become superficial at the back of the knee. Incompetence of a gastrocnemius vein, usually the medial, may cause swelling and discomfort within the calf yet nothing is apparent. Awareness may be precipitated by attempting to wear tight fitting boots or trousers when the difference in calf circumference is recognised yet there is no ankle oedema. Next a venous flare or dilated venules appear over a perforator site, usually the mid-calf perforator, but sometimes the Boyd's perforator, filling the posterior arch tributary of the greater saphenous vein. Incompetence of a gastrocnemius vein is suggested by the history and clinical examination. Reflux is demonstrated by Doppler ultrasound and accurately localized by duplex ultrasound with colour-flow imaging. The anatomy is clearly visualized by venography.Large gastrocnemius veins are seen in athletes and ballerinas with well-developed calf muscles and such veins are physiological and should not be interrupted. It is imperative that reflux is demonstrated before surgical treatment is offered. Treatment involves ligating the incompetent gastrocnemius vein through a small incision over the popliteal fossa. If the mid-calf perforator is also incompetent it is divided deep to the fascia through a small vertical incision and the fascial defect closed. The distal short saphenous vein may be removed by partial stripping and any tributaries removed by phlebectomies using Oesch hooks. Strong below-knee stockings are worn for a month following this surgery.