At the time the Panel met, the most impressive evidence linking the Type A behavior pattern to coronary heart disease was the prospective Western Collaborative Group Study (WCGS), which established a significant risk ratio for Structured Interview-assessed Type A behavior pattern for all clinical manifestations of coronary heart disease; and three angiographic studies which reported significant associations between Structured Interview-defined Type A behavior pattern and severity of coronary artery disease. Supporting evidence was provided by prevalence studies employing the Jenkins Activity Survey (JAS) measure of Type A behavior pattern, and by incidence and prevalence data from the Framingham study, using a six-item scale thought to assess aspects of Type A behavior.