The relationship of attitude to behavior is investigated through improvement in attitude measurement and the use of multiple variable analysis. The certainty of response to attitude items was used as a moderator variable to produce better attitude measurement. Regression analysis was used to consider the relation of a number of relevant personal and social variables to attitude, behavioral intention, and behavior. Data supporting the interpretation that certainty identifies individuals with developed attitudes are presented. Analysis of the relation of attitude and other variables to behavioral intention and behavior suggests when respondents are certain of attitude item responses, attitude is a major predictor of behavior and behavioral intentions, and additional personal and social variables fail to markedly improve behavior prediction. These findings are discussed in relation to selected aspects of Fishbein's (1967) analysis of the relation of attitude to behavior.