The "Phoenix phenomenon" as first noted by Collee et al. (1961) was investigated for Clostridium perfringens HT₉ and HT₁₀. The "Phoenix phenomenon" is described by an initial decrease in counts (Phase I), followed by an increase to the initial level of counts (Phase II), and continued increase above the initial counts to give maximum counts (Phase III). Under similar conditions as employed by Collee et al. (1961), the "Phoenix phenomenon" was reproduced for C. perfringens HT₉ and HT₁₀ at 51.7 C and 51.5 C, respectively. The effect of sporulation, age of inoculum, anaerobiosis, assay medium, growth inhibitors, and diluent were studied. The "Phoenix phenomenon" was reproduced in experiments using sporulation negative mutants derived from HT₉, various ages of inocula, and under strict anaerobic conditions. Similarly, all of the assay media tested: sulfite-iron agar, tryptose-soytone-yeast extract agar, peptone-yeast extract agar, veal agar, and pre-reduced veal agar, gave the "Phoenix phenomenon". The presence of a DNA inhibitor at the minimum point of the growth curve (end of Phase I) had no effect on the appearance of the "Phoenix phenomenon" (Phase II), however Phase III was completely inhibited. This indicated that Phase I and II was an injury-recovery process. The type and temperature of diluent was varied and the results indicate that although temperature of diluent had no effect on enumeration, a veal diluent relieved some of the stress to the organism in giving a less pronounced Phoenix effect.