The risk of developing rest pain during a six-year period was studied in 224 non-diabetic patients with intermittent claudication. Both smoking and multiple arterial stenoses in the leg were significantly correlated with an increased risk of developing rest pain. In non-smokers and in those who had stopped smoking within one year after the initial examination, the cumulative percentage of patients without rest pain after six years was 92, and in smokers and those who stopped smoking after more than one year it was 79 (p less than 0.03 after adjustment for differences in the presence of multiple stenoses). In patients with single stenosis the cumulative percentage of patients without rest pain was 86, and in those with multiple stenoses 70 (p less than 0.05 after adjustment for differences in smoking habits). The results emphasize how important it is that patients with intermittent claudication do not smoke. The increased risk of rest pain associated with the presence of multiple arterial stenoses in the leg should be considered when making decisions concerning vascular surgery.