In order to estimate the rate of local complications of phlebography we studied a one-year series of 477 patients. Half of the patients were examined with a comparatively highly concentrated contrast medium and half with a more diluted one. Eight patients had local complications, verified by biopsy and/or thermography and plethysmography. One had a deep vein thrombosis, five had a superficial thrombosis and two had a skin necrosis. There were more complications after the use of the more concentrated medium, six against two. The frequency of clinically significant complications to phlebography is rather low, but high enough to warrant attention to the risks of the method. The concentration of the contrast medium should be as low as possible, and the time that the vessels are exposed to the chemical trauma as short as possible. A hypothesis is brought forward that skin necrosis with slow healing could be secondary to arterial thrombosis caused by extravasal contrast injection.