PURPOSE Although reactive telephone helplines for quitting smoking are increasingly popular in the United States, the characteristics of callers using this resource have not been adequately studied. The objective of this study was to describe the characteristics of the current smokers calling a national reactive telephone helpline (i.e., study population). DESIGN AND SETTING In this cross-sectional study, information was obtained from eligible participants telephonically. SUBJECTS The study included 890 adult current smokers who were new callers to a national reactive helpline. MEASURES The information collected included selected demographic and smoking-related characteristics. ANALYSIS The proportions of the above characteristics were analyzed. RESULTS There was a significant overepresentation of blacks, non-Hispanics, women, and urban residents, as well as poorer, older, less educated, and heavier smokers in the study population (p < .01 for all comparisons). CONCLUSIONS Reactive telephone helplines may be preferentially used by population segments who are disadvantaged or smoke heavily and thus are in greatest need for assistance. These helplines may therefore fill a much-needed niche in the marketplace of smoking cessation strategies.