A major limitation of studies on the parvovirus B 19, a causative agent of transient aplastic crisis, has been the absence of appropriate cell lines permissive for the virus. In the present study, a human erythroid leukemia cell line (JK-1) was shown to support B 19 virus DNA replication in vitro. Forty-eight hours after virus inoculation of JK-1 liquid cell cultures, the average number of B 19 genome copies was estimated at 3,000 per cell by DNA dot blot analysis. The addition of erythropoietin increased B 19 copy number to 10,000 per cell. The presence of replicative forms of the B 19 virus genome was genome was demonstrated by Southern blot analysis. Although persistent infection of B 19 virus was not observed in JK-1 cells, this culture system will be of value in elucidating the molecular basis of the erythroid specificity of parvovirus B 19.