Three types of laser: the Nd: YAG laser, CO2 laser and Er: YAG laser, have been used for various dental treatments since July 1996 in Comprehensive Dentistry, Niigata Hospital, The Nippon Dental University. In this study, the frequency of using each laser was examined for each category of dental diseases between July 1996 to June 2004. They were used in a total of 1, 158 cases, with a mean age of 49.5 years (range 12 to 81 years). The frequency of use of the Nd: YAG laser (Pulse Master 600 LE, Denics International), CO2 laser (Opelaser 03S, Yoshida Dental Mfg. Co.), CO2 laser (Opelaser 03S II SP, Yoshida Dental Mfg. Co.) and Er: YAG laser (Erwin, Morita Co.) were 605 cases (52.2%), 301 cases (26.0%), 249 cases (21.5%) and 3 cases (0.3%), respectively. Based on the results of this survey, various factors such as wavelength characteristics, specifications of equipment, the light guide system and operative ability had significant influences on the selection of laser equipment for each clinical treatment. It is important for effective and safe use of lasers in dental treatment to understand the characteristics of each type of laser equipment.