The purpose of this article is to investigate the association between the background characteristics of patients with severe fear of dental treatment who frequently avoid dental care and the degree of difficulty in treating them. At the time of initial presentation at a dental phobia clinic, each of 321 subjects was asked to complete the State-Trait Anxiety Inventory, the Dental Anxiety Scale, and a health questionnaire related to phobic objects. Subjects who rejected oral examination with a dental mirror were categorized as being severely difficult to treat, whereas those who were able to undergo examination were categorized as being moderately difficult to treat. In the statistical analysis, assessment items that were correlated with difficulty to treat were designated as independent variables for a logistic regression analysis. In the logistic regression analysis, significant correlations were observed for gender (male > female with adjusted odds ratio, 4.121; 95% CI, 1.96–8.65) and level of trait anxiety (2.401; 1.01–5.73). Male gender and a high trait anxiety were identified as major factors associated with severe dental fear and avoidance.