The JHM strain of murine hepatitis coronavirus is neurotropic in rats, causing either fatal acute encephalomyelitis or subacute demyelinating encephalomyelitis. We have examined the growth properties of three JHM virus isolates in primary rat glial cultures and found a correlation with their ability to cause disease. Wild type JHM virus has the propensity to cause lytic infections in glial cultures, and a temperature-sensitive mutant designated JHM-ts43 invariably produces persistent infections with reduced cytopathic effects (CPE) as compared to the wild type. Moreover, a non-neurotropic isolate, designated JHM-Pi virus, produces either non-productive persistent infections at low multiplicity of infection (m.o.i.) or productive persistent infections at high m.o.i., with, however, no CPE. The phenotypic expression of persistence is glial cell-dependent, since all three viruses produce similarly lytic infections when grown on various susceptible cell lines. The genetic basis of JHM virus persistence can be explained at the level of direct virus-glial cell interactions.