An examination of 1732 conventionally treated maxillary molars was made in an attempt to determine the percentage of MB2 canals that could be located routinely. The teeth examined were 1096 first molars, 611 second molars, and 25 third molars. The results were recorded on a modified computer program over an 8-yr period of time. An interesting trend was noted. The MB2 canal was found in 802 (73.2%) first molars, 310 (50.7%) second molars, and 5 (20.0%) third molars. It occurred as a separate canal in 54.9% of first molars, 45.6% of second molars, and joined in all third molars. However, as the operator became more experienced, scheduled sufficient clinical time, routinely employed the dental operating microscope, and used specific instruments adapted for microendodontics, MB2 canals were located in 93.0% of first molars and 60.4% in second molars.