The purpose of this study was to evaluate the potential for spreading bacterial contamination from the root canal to the patient and the dental team via the smoke produced by the laser. Five extracted teeth were deliberately inoculated with a specific strain of Escherichia coli. The canals were subjected to an agron laser. The smoke plume was captured and cultured. All of the cultures were positive for growth of the E. coli used. It was concluded that the laser smoke does present a hazard of bacterial dissemination and that precautions must be taken to protect against spreading infections when using lasers in the root canal.