According to a 1992 national survey, more than 95 percent of general dentists in the United States purchased malpractice insurance. The authors evaluated the survey findings to identify factors that had the greatest effect on dentists' insurance premium costs. Premiums were higher for dentists who had been the subject of previous complaints or claims, as well as for those who owned their practices. States with fewer lawyers had lower premiums. Finally, state limits on use of dental hygienists, number of offices and the extent of water fluoridation also affected premium levels.