Cigarette smoking is a major source of mortality and medical costs in the United States. More graphic and salient warning labels on cigarette packs as used in Canada may help to reduce smoking initiation and increase quit attempts. However, the labels also may lead to defensive reactions among smokers. In an experimental setting, smokers and nonsmokers were exposed to Canadian or U.S. warning labels. Compared with current U.S. labels, Canadian labels produced more negative affective reactions to smoking cues and to the smoker image among both smokers and nonsmokers without signs of defensive reactions from smokers. A majority of both smokers and nonsmokers endorsed the use of Canadian labels in the United States. Canadian-style warnings should be adopted in the United States as part of the country's overall tobacco control strategy.