A continuous cell line derived from kidney tissue of the African green monkey, Cercopithecus aethiops and designated BS-C-1, has been maintained through 142 subcultures. Cultures of the BS-C-1 line support the growth of simian virus 40 to the same extent as do primary Cercopithecus kidney cell cultures; moreover, the pathognomonic vacuolating changes induced by this virus are as apparent in the continuous cell line as in the primary cell cultures. The BS-C-1 cell cultures are suitable for propagating several viruses, including polio, measles, Rift Valley fever, respiratory syncytial, Coxsackie A9, O'Malley's A-1 agent, and simian agents 1, 4 and 5. In contrast, several strains of influenza A and B viruses and of adenoviruses 3, 4 and 7 as well as simian virus 2 failed to multiply in BS-C-1 cells.

No change in the susceptibility of the BS-C-1 cultures of SV₄₀ virus was detected throughout 142 passages of the cell line. On the other hand, during this period of culture the cell line changed its chromosomal characteristics. Thus, the pattern remained diploid, i.e., 60 chromosomes, beyond the 20th subculture, and became subdiploid by the 41st passage after which it continued to change its characteristics with a majority of the cells in the 52nd passage having 59 chromosomes and the remainder 58; most of the cells had a dicentric chromosome. By the 111th passage, most of the cells approached the hypotetraploid state with 83% of the cells having 114 to 117 chromosomes. To our knowledge, this represents the first instance in which continuous observations have been made on the susceptibility of a tissue culture cell system to a given virus during a period when its cells changed from the diploid to the polyploid state. In this particular system the changes in chromosomal pattern were not associated with change in susceptibility to the virus. The BS-C-1 line is apparently free of extraneous microbial agents; seed cultures can be maintained in the frozen state; it grows rapidly and is not fastidious in its nutritional requirements.

The BS-C-1 continuous cell line provides the virologist with another tool for diagnostic and research work and perhaps for the large scale cultivation of viral agents for vaccines. As regards the last mentioned possibility the employment of continuous cell lines has recently received a cautious endorsement (22) for use in carefully planned, progressively expanding studies.