Outcome expectancies are central to a social learning model of smoking and of smoking cessation. The Smoking Effects Questionnaire (SEQ) was developed for use in general adult populations. Items were administered to 257 smokers and ex-smokers including worksite employees, hospital visitors, and clients entering smoking cessation treatment. Principal components analysis (PCA) found seven components with good reliability that were reduced into scales of four or five items each with internal consistencies above alpha=.80. The final measure has 33 items. The scales were divided by secondary factor analysis into three negative effect and four positive effect scales. The SEQ showed good construct and concurrent validity in comparison with measures of similar constructs and with other smoking variables. Women expected fewer negative physical effects and attributed more importance to positive stimulating effects from smoking but otherwise were comparable to men in expected effects of smoking. More dependent smokers ascribed more importance to negative physical effects and positive stimulating effects than did less dependent smokers but did not differ significantly on other expectancy domains. Both true/false scoring and importance ratings of effects produced mostly comparable results so that either scoring method could be used. Treatment implications were discussed. This brief scale is likely to be useful in a variety of research and clinical settings.