Bier's method of regional anaesthesia has been proposed to deposit various drugs intravenously distal to an arterial block in legs with severe arterial insufficiency. From the theoretical point of view it is assumed that ischaemic acral skin areas while being cut off the arterial blood supply may still be reached on the venous route. The purpose of this study was to test this hypothesis for different injection techniques using sodium fluorescein as tracer. Measurements were carried out in ten patients with intermittend claudication. After a circulatory arrest according to v. Esmarch had been established a total volume of 100 ml was injected into a peripheral vein at either the calf or foot. In five patients a homogenous fluorescein mixture was prepared prior to the injection ("cocktail"-group) whereas the other five received an isolated fraction of 10 ml fluorescein ("fraction"-group). Subsequently, the fluorescence distribution at the calf and dorsum of the foot was photographically recorded over a period of 20 minutes and evaluated by means of digital image analysis. Fluorescence rapidly and homogeneously spread over the investigated skin areas including the toes in all five cases of the "cocktail"-group. In contrast, a rather delayed and heterogenous fluorescein distribution was observed in the "fraction"-group. Furthermore, in two cases no dye could be detected at the digits after 20 minutes. These results have confirmed the hypothesis of RVP provided that all ingredients are dissolved within an adequate amount of fluid prior to injection.