The fundamental practical premises underlying the practice of intensive psychotherapy are investigated in this article. Based on ego-psychology orientation, mental illness is classified in terms of premature ego development, ego distortions, ego deviations, ego regression, and ego defects. General healing factors are reviewed, first as presented, for example, in Frank's "demoralization hypothesis." The forms of psychotherapy may be classified in terms of how they approach the problem of demoralization and failure of ego adaptation, into counseling, supportive, reeducative, and psychoanalytic. Intensive psychotherapy is conceived of as a derivative discipline of psychoanalysis. It is different in that the goals are more limited, and active interventions ("parameters" or "departures") are often unavoidably called for, making it less "neat and orderly," more taxing on the therapist, and more of an art. It is similar in that an emphasis on the patients' spontaneous associations and an attempt to retain analytic neutrality as much as possible leads to the formation of transferences and resistances which may be dealt with by interpretation. However, full-blown transference neuroses usually do not form as in classical psychoanalysis, limiting the depth and extensiveness of the procedure. Intensive psychotherapy is the treatment of choice for selected cases of schizophrenia, severe personality disorders, and psychosomatic conditions.