Human limbal explants obtained from 44 eyebank donors were cultured in medium 199 supplemented with 20% fetal bovine serum, vascular endothelial cell growth supplement and heparin. Cells grew abundantly out of the explants. They initially formed a 'cobblestone' patterned monolayer but later exhibited an elongated morphology with growth in parallel bundles. These cells could be passaged at least nine times and were identified throughout the consecutive passages as microvascular endothelial cells by the expression of factor VIII-related antigen, laminin and of the H determinant of ABO blood groups. As expected from vascular endothelial cells, flow cytometric analysis demonstrated a strong expression of class I histocompatibility antigens and a weaker expression of class II antigens. Class II antigen expression was enhanced by culturing the cells in the presence of immune interferon. These cells produced immunoreactive interleukin-1, mainly of the alpha type, under endotoxin stimulation. Limbal microvascular cells could be useful to study corneal angiogenesis. Furthermore, long-term culture of limbal cadaveric tissue can potentially be used to characterize donor-specific immunologic responses in corneal graft recipients.