Three methods of assessing smoking status among newly diagnosed cardiovascular (CV) patients were compared: self-reports, collateral reports (spouse, friend, etc.), and saliva cotinine assays. Self-reported smoking status was assessed as the average number of cigarettes smoked per day at baseline, 3, 6, 9, and 12 months into treatment, and at a 6-month posttreatment follow-up. The majority of patients had quit smoking within 6 months prior to participating in the program. All participants were informed at the onset of the study and at the time of each assessment that their self-reports of smoking abstinence would be validated through collateral reports and possibly saliva cotinine analyses. Less than 5% (13 of 274) of the subjects' self-reports showed discrepancies with collateral reports. Analyses of saliva cotinine assays in a subsample of subjects, however, indicated that 16% (13 of 81) of the saliva cotinine tests were discrepant with the collateral reports. Thus, the saliva cotinine analyses picked up an additional 11% false negatives, as compared to collateral reports. It is concluded that the use of collateral reports as an index of smoking status may be an overestimate of actual quit rates. The overall discrepancy rate for this study, however, was fairly low and suggests that patients' self-reports may be reliable when they have already quit on their own and/or are notified in advance of verification procedures.