One study suggested that the use of two placebos in a control group may produce higher smoking-cessation rates than the use of a single placebo.25 This might account for the smaller difference in the long-term rates of smoking cessation between the placebo group and the nicotine-patch group in our study. The weak effects, however, seem unrelated to prior use of the nicotine patch. The rate of previous use of a nicotine patch was similar among the four groups. In the nicotine-patch group, there was no significant difference in the rates of continuous abstinence at 12 months between subjects who had previously used patches and those who had not (8.6 percent vs. 10.6 percent, P=0.61).