Marshall, Ronald G. (Army Chemical Corps, Fredrick, Md.), and Peter J. Gerone. Susceptibility of suckling mice to variola virus. J. Bacteriol. 82:15–19. 1961.—The susceptibility of suckling mice inoculated intraperitoneally or intracerebrally with variola virus was investigated. Data are presented that define the death patterns, the relationship of incubation period to dose of virus inoculated, the multiplication of virus in suckling mice, and the influence of the age of suckling mice on their susceptibility to this virus. Additionally the results indicate that a variola virus neutralization test is feasible using the young suckling mouse as an indicator host.