The distribution of vessels in normal human synovium has been investigated using frozen sections and staining with Ulex Europaeus lectin by an indirect immunoperoxidase technique. The presence of a vascular net close to the tissue surface was confirmed. Quantitative analysis showed the majority of vessel profiles to be small venules with a peak density 25-100 microns beneath the tissue surface. A smaller number of capillaries was present with a peak density within 25 microns of the tissue surface. It is suggested that important functions of the numerous venules seen in synovium may include the provision of a source of fresh monocytes to replace surface macrophages and provision of nutrients for the surface layer of cells as a whole, and that the density of the vascular net may reflect angiogenic signals from this cell layer.