The role of incompetent perforating veins in the aetiology of varicose veins is not well understood. Anecdotally, competitive cyclists appeared to be more prone to varicose veins than the general population. We present a case of a 63-year-old amateur competitive cyclist who acutely developed a painful varicosity of her left calf while straining during a hill climb in 106-mile cycle race. Duplex ultrasonography has shown an underlying incompetent perforating vein, feeding the varicosity directly through the underlying muscle. With no other significant venous reflux in either leg, we believe this case shows a clear causative association between the stresses put across the lower leg during competitive cycling and developing a varicose vein via an incompetent perforating vein. We believe this should lead to further investigations as to any link between cycling, perforator vein incompetence and the development of varicose veins.