To investigate the accuracy of offspring assessments of parental smoking status, we studied 116 parents and 151 adult children (276 parent-child dyads) who provided data on both their own and their parents' smoking status. All currently smoking and all ex-smoking parents were correctly classified as ever-smokers by their offspring (n = 79 and 100, respectively). Of the 97 offspring who reported on never-smoking parents, 88 correctly classified their parents as never-smokers. Thus, sensitivity for detecting ever-smoking in parents was 100%, and specificity, 91%. Because all incorrect classifications involved never-smoking parents, further analyses focused on this group. Too few parents were misclassified to permit testing of parental characteristics. Offspring who misclassified their parents were significantly older than those who did not; neither sex nor smoking status of the offspring was associated with the increased likelihood of misclassification. No significant differences were discovered for dyadic factors (concordance/discordance for sex; parent-offspring age difference). Overall, these results support the utility of proxy reports of parental smoking phenotype by adult informants when self-report is unavailable.