The sales of the lowest yield cigarettes (1-3 mg tar) seem to have been particularly resistant to the effects of promotion and advertising, while the sales of other low-yield cigarettes (4-9 mg tar) seem to have been increased by promotional efforts. This finding is consistent with the existence of a boundary of tar and nicotine acceptability below which consumers in general are not prepared to go. Use of lower tar cigarettes may be helpful for those who cannot stop smoking, but, since 1979, the percentage of cigarettes under 16 mg tar has changed little.