Half a century ago, on January 11, 1964, the U.S. Surgeon General's office released a landmark report on the health consequences of smoking. That report received massive media attention and triggered a steadily growing number of federal, state, and local restrictions on the advertising, sale, and use of cigarettes. Little is known about the report's impact on American public opinion because all the timely public opinion polls that measured the report's impact were privately commissioned by the tobacco industry and were not made publicly available. A review of these polls shows that the 1964 Surgeon General's report had a large and immediate effect on Americans' beliefs that cigarettes were a cause of lung cancer and of heart disease. However, the report had less impact on public preferences for government action or on smoking rates.