Monkey pox virus was mechanically disrupted by low temperature and high pressure into soluble and insoluble fractions. Soluble fractions elicited virus-neutralizing antibodies (1:20 to 1:160) in rabbits, whereas the insoluble (in saline) fractions did not (less than 1:5). No infectious virus was detected after the disruption procedure. Rhesus monkeys immunized with the soluble fraction elicited virus-neutralizing (1:1,200), complement-fixing (1:16), and hemagglutinating-inhibiting (1:80 to 1:160) antibody titers and were completely protected against monkey pox virus-induced disease. This model of monkey pox virus subunit vaccine preparation may prove to be useful in developing an efficacious noninfectious vaccinia vaccine for use in high-risk individuals.