Cultures of rat lung microvascular endothelial cells (RLMECs) were obtained from perepheral lung tissue. The lung tissue was cut into small pieces and cultured with RPMI-1640 containing 20% bovine calf serum, 90 micrograms/ml heparin, 4 mmol/L L-glutamine, 100 mu/ml penicillin and 100 micrograms/ml streptomycin. Erythrocytes and leukocytes left the tissue first, followed by RLMECs. Fibroblasts and other cells grew after 72 hours of culture. After 60 hours of culture, the lung tissue was discarded. RLMECs in flask showed regular cobblestone morphology and positive for binding of the lectin Bandeiraea simplicifolia I and indirect immunofluoresence staining with factor VIII antiserum.