Worksite smoking cessation intervention programs have become increasingly popular, although program evaluations are often unavailable. In 1984, the Texas Operations of Dow Chemical USA offered a Smoking Cessation Incentive Program (SCIP) to its employees. SCIP was a highly publicized, upbeat program that had the active support of management and union. Altogether, 7,516 employees (95.4% of all employees) were surveyed about their smoking habits; 28.3% identified themselves as smokers. A total of 1,113 employees voluntarily enrolled in SCIP from March 1, 1984, through March 1, 1985. Smoking cessation methods included a buddy program, nicotine-containing chewing gum, American Lung Association self-help material and group clinics, and incentive prizes. SCIP registrants, compared to employees identified as smokers in a pre-program survey who did not participate in SCIP, were significantly (P less than .01) more often females, whites, administrators, professionals, heavier smokers, and smokers who had tried to quit at least two times prior to SCIP. There were 326 (29.3%) SCIP participants who quit smoking for at least one month during SCIP. A total of 265 (23.8%) succeeded at quitting for at least six months and remained ex-smokers at the end of the program. Logistic regression analysis showed administrators had significantly higher six-month or more rates of quitting than did professionals, craftsmen, operators or clerical workers.(ABSTRACT TRUNCATED AT 250 WORDS)