Initial psychometric evaluation of an instrument to measure perceived benefits of exercise and perceived barriers to exercise was based on the responses of 650 adults and included item analysis, factor analysis, and reliability measures. Factor analysis yielded nine factors, five benefits and four barriers, which explained 64.9% of the variance in the 43-item instrument. Second order factor analysis resulted in a two-factor solution, one a benefits factor and the other a barriers factor. The standardized Cronbach's alpha reliability coefficients were: 0.952 for the total scale, 0.953 for the benefits scale, and 0.886 for the barriers scale. Use of the instrument in research involving perceptions of the benefits of exercise and the barriers to exercise appears warranted.