A simple topographic method has been developed for the localisation of the venous angle on the lateral cerebral phlebogram. The principle depends on an angular measurement and an estimation of proportions which are statistically independant of each other. The method was tested on 103 phlebograms of adult patients with supratentorial spaceoccupying lesions. It was compared with conventional measurements; a number of advantages were found for using our method and its accuracy is as good as the other, most precise, methods.