Self-help materials computer-tailored to the specific needs of smokers have shown promise as a high-reach, low-cost intervention for smoking cessation. Adding tailored cessation materials to telephone-based cessation counseling may be a way of generating greater efficacy in promoting and maintaining cessation. The objective of this study is to assess the efficacy of adding different types of behavioral smoking cessation materials to brief telephone-based cessation counseling.A total of 1,978 smokers calling the National Cancer Institute's (NCI's) Cancer Information Service (CIS) for help in quitting smoking initially received brief cognitive-behavioral cessation counseling from a CIS information specialist. Following a baseline interview administered by the information specialist, subjects were randomly assigned to one of four conditions, each delivered by U.S. mail: a single, untailored smoking cessation guide (SU); a single, tailored smoking cessation guide (ST); a series of four (multiple) printed materials tailored only to baseline data (MT); and a series of four (multiple) printed materials tailored to baseline as well as retailored using 5-month interim progress data (MRT). The primary outcome measure was 7-day point prevalence abstinence rates assessed using a computer-assisted telephone interview (CATI) at 12-month follow-up.At 12-month follow-up, using intent-to-treat, imputed, and per-protocol analyses, no differences were found among the four experimental conditions (linear trend), or when the ST, MT, and MRT groups were compared with the control (SU) group. Participants in the two multiple message group conditions combined (MT + MRT), however, had significantly higher abstinence rates than participants in the two single message group conditions combined (SU + ST). Moreover, among subjects who reported quitting at the 5-month follow-up, participants receiving the MRT materials reported higher abstinence rates at 12 months than the other three groups combined (SU + ST + MT). The results of this study support the effectiveness, over and above a single telecounseling interaction, of multiple tailored print material contacts on cessation. These effects, however may be due to tailoring, or the longitudinal nature of the two multiple tailored conditions, or both. The strongest evidence for tailoring occurred in the MRT condition for relapse prevention, suggesting that print materials tailored to interim progress may be especially effective in this context. The qualities of specific psychosocial and communication elements in tailored materials should receive attention in future research.