A microscopic study is presented on the depth distribution of the microvessels in the scalp of two human fetuses at term. The basal membrane showed a smooth line without papillary structures resulting in a thin epidermal layer of 25 microns. The distance from the scalp surface to the periosteum appeared to be almost 1.8 mm. The capillary density showed a peak of approximately 1.2 capillary cross-sections per 10(4) microns 2 in the first 200 microns of the dermis. In the middle of the dermis the capillary density fell to 0.2 cross-sections per 10(4) microns 2 to rise again in the lower part of the dermis to 1.6 cross-sections per 10(4) microns 2, which remained the approximate count in the subcutaneous tissue. The arterioles and venules showed significant numbers in the lower part of the dermis and were virtually absent in the subcutis. Of all 4570 microvessel cross-sections that were studied in a tissue volume of 0.6 mm3, not a single one showed the features of an arteriovenous anastomosis. The possible implications for laser Doppler flowmetry and continuous blood gas measurement of the fetal scalp are discussed.