Thirty five patients, most of them athletes, with chronic Achilles tendinopathy were enrolled in a study of tendon blood flow using laser Doppler flowmetry at rest and during physical provocation by passive stretch and contraction of the triceps. The patients were compared with a group of 40 healthy volunteers assessed according to a similar protocol in a previous study. In both groups values were significantly lower at the distal insertion, but otherwise the values were evenly distributed throughout the tendon. Blood flow in the symptomatic tendons was significantly elevated as compared with the controls. Both groups demonstrated a similar vascular response to physical loading, a progressive decline in blood flow as tension increased. Contrary to popular belief chronic Achilles tendinopathy is associated with an increased blood flow of uncertain origin. A local deficiency in tendon blood supply does not initiate the lesion nor does it explain why the condition persists.