This article presents concepts, problems, and approaches used in a completed observational study carried out by 47 therapists in analytical/psychotherapeutic private practices and institutions. The diagnostic situation (of 739 patients) and the initial phase of therapy (involving 381 patients) were studied with the help of a comprehensive system of documentation. What is documented here is the patient perspective on the one hand and the perspective of the therapists on the other with regard to numerous self-evaluations and evaluations by others, evaluations that throw light on the diagnostic-therapeutic process from different observational levels. Most of the scales used were developed in the study group. Given the complex structure of the data, new methods of storing and evaluating data had to be found. In addition to the description of the therapeutic reality of a large city, the main goal of the study was to examine the patient-therapist relationship and the prognostic elements it contains since these elements influence the indication for psychotherapy and the possibility of its successful realization and thus have the character of predictors for the course of psychotherapy. A number of other results of the study are presented in the succeeding contributions to this issue.