Gutta-percha cones were contaminated with pure cultures of Staphylococcus epidermidis, Corynebacterium xerosis, Escherichia coli, Streptococcus faecalis, and Bacillus subtilis. The cones were then immersed in undiluted Clorox (5.25% sodium hypochlorite) for variable periods of time. All organisms except B subtilis were killed after a 30-second exposure to Clorox. The vegetative form of B subtiliswas killed after a 45-second immersion time whereas the spore form of this microorganism required a one-minute sterilization period. The data indicate that gutta-percha cones may be sterilized, in all cases, by a one-minute immersion time in undiluted Clorox.