Using responses to 3,315 survey questions asked of national samples, we examine how policy preferences of Americans have changed over the last 45 years. The data indicate that there has been considerable stability in public opinion: responses to half the 613 repeated policy items show no significant change at all; approximately half the detectable changes were less than 10 percentage points; and rarely did preferences fluctuate significantly back and forth within a short time period. Foreign policy changes were no larger or more frequent than domestic, but they did tend to occur more abruptly. When opinion shifts occurred, they were not random or capricious; they were usually related to important changes in citizens' social and economic environments. Rapid shifts generally coincided with major events in international affairs or the economy.