The Purpose of this article is to describe application of the Theory of Reasoned Action(TRA) to Nursing. Modern expectancy theories have evolved from two areas of research ; social-psychological investigations of the relationships between attitudes, beliefs, and behaviors and behavioral decision theory. TRA derived from social psychology, predicts a person`s intention to perform a behavior in a well defined setting. The Theory can be used to explain virtually any behavior over which an individual has volitional control. The model assumes that behavior and that all other factors that influence behavior are mediated through intention. The measurement of intention must closely correspond to the measurement of behavior in terms of the action, target, context, and time in order to accurately predict behavior. The strength of person`s intention to perform a specific behavior is a function o two factors : attitude toward the behavior and the influence of the social environment or general subjective norms on the behavior. Attitude toward the behavior is determined by and individual`s belief and an evaluation of the outcome. Social norm is determined by a person`s normative belief about what salient others think he or she should do and by the individual`s motivation to comply with those people`s wishes. *Application researches of the Theory of Reasoned Action : 1. Operationally Defining the Theory of Reasoned Action to Predict Condom Use ; The purpose of this study is operationally define to various terms of TRA. The subjects were patients in a sexually transmitted disease(STD) clinic. The used of condoms is instrumental in primary prevention of STDs. Since the risk for contracting STDs depends almost exclusively on an individual`s behavioral choices, understanding the determinants of sexual decision making has important implications for the design of health education interventions. Salient outcomes used to develop the study questionnaire were identified from interviews and an open-ended questionnaire the study questionnaire were identified from interviews and an open-ended questionnaire with representative sample of 40 STD clinic patients. The model`s variables, attitude toward the behavior and subjective norms were measured on seven-point bipolar rating scales and appropriate wording modifications were made for male and female patients. In this study, both attitude toward condoms and general subject norm significantly predicated intention to use condoms for both steady and new or infrequent partner. 2. Predicting breast Self-Examination Using the Theory of Reasoned Action : The personal and normative influences on breast self-examination(BSE) behavior in older women were examined using the TRA. Direct and indirect measures of attitude and social norm wee used to predict intention to predict intention to perform BSE and BSE frequency. Both the indirect and direct measures of attitude and social norm explained a significant amount of the variance in intention and BSE frequency. In conclusion, TRA is useful in the prediction of health providers to develop intervevtions and strategies for change that will be maximally effective.