PURPOSE: The Transtheoretical Model is a theory-based approach for conceptualizing behavioral change. Inherent in this model is the determination and use of appropriate interventions to assist clients in improving their health behaviors. In the Transtheoretical Model, behavioral change progresses through a series of stages (precontemplation, contemplation, preparation, action, and maintenance) where movement from stage to stage is dependent upon decisional balance (the pros and cons that influence the decision). The purpose of this study was to develop instruments to test the validity and reliability of two components of the Transtheoretical Model–stages of change and decisional balance–as they relate to a new application in oral self-care behavior. An additional purpose was to determine if there was an association between these two components that would be applicable to a specific oral self-care behavior. METHODS: A three-part questionnaire was developed consisting of 1) stages of change instrument (4 items), 2) decisional balance instrument (40 items), and 3) demographic and dental experience information (9 items). Regular interdental cleaning was chosen as a behavior representing a commitment to oral self-care. The study population consisted of 709 subjects aged 35 to 55 who were recruited from 17 dental practices. RESULTS: A 70% (n = 521) response rate was obtained. Based upon the stages of change portion of the questionnaire, nearly 60% (n = 309) of the subjects were in the maintenance stage, while 21% (n = 109) were in precontemplation, with the rest distributed among the other stages. Reliability of the instrument was established with Kappa scoring. The decisional balance instrument was subjected to factor analysis resulting in a final decisional balance instrument of 28 items. There was a statistically significant relationship between the two components of stages of change and decisional balance. CONCLUSIONS: Stages of change and decisional balance instruments were developed and shown to be valid and reliable. Based upon the oral self-care behavior defined in this study, these instruments can identify an individual’s current behavior and assess readiness to change by analyzing the distribution of the pros and cons a person considers when making a behavioral change. Understanding a client’s behavioral stage would enable the practitioner to select and provide appropriate interventions. Further research should focus upon development of stage-appropriate intervention strategies and techniques, in order to move individuals along the continuum of stages toward behavioral change. Additionally, research with parallel and diverse populations is indicated.