In continuation of a recently-published investigation on the effect of intramuscular injections of an ozone-oxygen mixture on experimental gas gangrene in the guinea pig, 2 additional experiments were performed in order to establish the efficacy of the therapy when given twice daily instead of only once. Futhermore, the effect of an analogous therapy was investigated with the use of pure oxygen. The ozone-oxygen therapy reduced the death rate from 100% in untreated control animals to 73.6 and 70.0%, respectively, in the 2 series of experiments. The median survival times were prolonged from 0.56 and 1.33 days to 5.50 and 6.66 days. The use of oxygen twice daily reduced the death rates significantly even further to 57.0 and 47.9%. With this therapy the median survival time was increased to 8 and more than 12 days. The differences in therapeutic effect of the 2 gases were not, however, statistically significant. On account of its simple applicability previous experiments on animals it is proposed that this therapy be employed also in cases of human gas gangrene. In addition, the bactericidal effect of CaCl2, as used in this experimental study, on vegetative forms of Clostridia is demonstrated.