The purpose of this study was to develop a valid and reliable instrument to measure the Social Cognitive Theory (SCT) constructs of smoking refusal skill-efficacy, positive smoking refusal outcome expectations & importance and negative smoking refusal outcome expectations & importance. This article details the rigorous instrument development procedure in which the instrument (1) reflects the learning objectives of a psychosocial smoking prevention program (2) reflects the SCT which the program was based on and (3) had adequate sensitivity to capture variation in student responses. A two-stage panel review established face validity. Instrument stability using test retest methods (Pearson r: P less than 0.002) and internal consistency (Cronbach's alpha: 0.74-0.97) were established. Construct validity was tested with confirmatory factor analysis, 57 of the 62 instrument items loaded as hypothesized.