The paper examines trends in daily smoking of U.S. high school students, along with smoking-related attitudes and beliefs. Data are drawn from surveys of high school seniors from 1978 through 1995, conducted by the University of Michigan's Monitoring the Future Project (a nationally representative sample of 15,000-18,000 students per year). Diffusion theory furnishes the conceptual foundation to assess the spreading acceptance of cigarettes within the cohort. The proportion of students who had ever smoked on a daily basis declined from the late 1970s through the early 1990s but has increased annually since 1992. The proportion trying cigarettes has increased, as has the proportion of smokers who escalate to greater frequency. The grade in which smokers first reach daily frequency has shown a marked upward shift in the later high school grades, a change which appears to be connected with the delaying effects of school intervention programs, among other factors. The overall upswing in daily smoking is connected with greater social acceptance of smoking and lower perceived risks.