SUMMARY

Various mammalian cells propagated in serum-free and chemically defined media yielded high titres of Venezuelan equine encephalomyelitis viru. Some difference in maximum titres was noted, depending upon the medium employed. Of the two serum-free media tested, lactalbumin hydrolysate medium was more effective than the chemically defined medium in supporting virus growth. The addi-tion of serum to serum-free cultures at the time of virus inoculation had a pro-nounced effect characterized bya delay followed by a burst of virus replication to very high titres. Thus, the degree of replication of Venezuelan equine encephalo-myelitis virus appeared to be influenced by a variety of unknown nutritional factors