Hepatitus A virus is grown in Vero cells after passage in in vitro cell culture. Virus replication and continued passage in Vero cells requires extended incubation times, up to about four weeks, for early passages and incubation temperatures no higher than about 32.degree. C. Continued passage results in a significant decrease in incubation time and an increase in virus yield. Cultivation of hepatitus A virus in Vero cells meets the development requirements for an inactivated human vaccine.