Fifteen micrometres radiolabelled dextran spheres were injected into three adult monkeys; after measuring reference flows, the animals were killed and biopsies were taken from skin and 15 oral mucosal regions. These were weighed, the radioactivity counted and a blood flow calculated as ml/min per 100 g tissue; the area and volume of each biopsy were also determined and blood flows re-calculated on a per area and per volume basis to determine the effect of changing the method of expressing flow. The flow to the different oral regions did not show any significant differences in rank order when expressed on these different bases. Four regions, maxillary and mandibular free gingiva and anterior and posterior dorsum of tongue, showed significantly higher blood flows than all other regions; skin showed a lower flow than the majority of oral regions and palate the lowest of all regions.