Previous studies of assessment of change, especially those of Hartmann and Jones, are discussed at length. The author and his collaborators' research uses three sets of variables—patient, treatment, and situation. The first and third are self-explanatory. The second includes, in part, technical interventions, attributes of the therapist, and the climate within which patient-therapist interaction takes place. Assessments are taken at various points in time. The project described is an inquiry into the nature of the psychotherapeutic process through assessment of changes and the interrelations of changes among all the selected variables.