Data previously reported (Garfield, 1978) on the number of clients/patients appearing at psychotherapy sessions from intake to termination did not identify the attritional features of service delivery systems. These earlier studies were retabulated and new data were accumulated from several contemporary sources: a university counseling center, an outpatient alcoholic treatment center, and a Health Maintenance Organization. The distribution of the flow of cases from intake onward was plotted and revealed the same shaped curve as found in the replotted literature reviews, i.e., a negatively accelerating, declining ("decay") curve, a Poisson Distribution. The means and standard deviations, while different from one clinic to another, showed similar values within each clinic. The attrition curve presents a general, descriptive curve embracing the entire flow of cases from admission to termination. This general, descriptive framework reveals the need for further research into whether clients drop out of therapy because of perceived success or lack of success, and why some cases take longer. Follow-up research must begin with a description of the attrition curve as a necessary baseline before any intervention can be meaningful. (JAC)