The Experience Sampling Method (ESM) is a research procedure for studying what people do, feel, and think during their daily lives, It consists in asking individuals to provide systematic self-reports at random occasions during the waking hours of a normal week. Sets of these self-reports from a sample of individuals create an archival file of daily experience. Using this file, it becomes possible to address such questions as these: How do people spend their time? What do they usually feel like when engaged in various activities? How do men and women, adolescents and adults, disturbed and normal samples differ in their daily psychological states? This chapter describes the Experience Sampling Method and illustrates its use for studying a broad range of issues.The origins of interest in daily experience and the origins of the method can be traced to numerous sources within the field of psychology. One of the earliest spokespersons for the scientific study of everyday life was Kurt Lewin (1935Lewin ( , 1936, who advocated investigation of the ''topology'' of daily activity. He believed that, by examining the psychological life space, it would be possible to understand the forces that structure daily thought and behavior. Regrettably, Lewin did not have a method for studying daily experience, and his American followers (for example, Roger Barker, Herbert Wright, P. V. Gump) turned to a behavioral H. T. Reis (Ed.), New Directions for Methodology of Social and Behavioral Sciences (vol. 15,. San Francisco: Jossey-Bass. Ó 1983 Wiley imprint-Republished with permission.