The rates (after 12 months' follow-up) of unassisted smoking cessation reported in the literature have varied from 13.8 per cent to 8.5 per cent. A meta-analysis was conducted of the abstinence rates observed in 14 samples of smokers who presented at primary health settings and received either no intervention aimed at smoking or usual care (which involved no deliberate intervention for smoking cessation). The estimated rate of stopping smoking without intervention, over an average 10-month period, was 7.33 per cent. This rate is consistent with others reported in the literature when motivation to quit is taken into account. The estimate provides a baseline to judge the effects of smoking-cessation interventions.