Using the F.D.A. method of testing germicides, the bactericidal propertiesof two cationic detergents, "Cetavlon" and "Fixanol C," were tested againstten organisms at seven pH levels betwee::l 5.2 and 8.2. The results for thetwo detergents were similar. Gram-positive organisms were more susceptiblethan Gram-negative. There was considerable variation in the'relationship betweensusceptibility and pH. Staph. aureus, Staph. albus, Strep. faecalis, andProteus vulgaris were all most suceptible under slightly alkaline conditions;whereas Ps. fluorescens, Ps. pyocyanea, Achromobacter Uquefaciens, and Bacteriumcoli were most susceptible under slightly acid conditions. The susceptibilityof Corynebacterium equi was unaffected by pH within the rangestudied.