Measles virus (MV) RNA is present in endothelial cells (Ec) in brain tissue from cases of subacute sclerosing panencephalitis (SSPE) and relatively high titres of infectious virus are produced in human cerebral Ec in vitro. Infection of Ec at the blood-brain barrier could therefore provide the opportunity for entry of virus to the CNS. Adhesion of syngeneic splenocytes to MV infected murine (Balb/c) cerebral Ec is found to be upregulated. Increased expression of endothelial adhesion molecules, following virus infection at the blood-brain-barrier, may be an important mechanism in inducing inflammatory infiltration of the CNS in SSPE.