In 1911 the extent and limitations of the utility of sanatorium treatment of tuberculosis were already fairly well recognized by physicians; and it is unfortunate that in connection with the passage of the National Insurance Act this treatment acquired a somewhat political aspect, and became the subject of much popular misapprehension and exaggeration. Disappointment necessarily followed on the sending of patients to sanatoria for treatment with a view to cure at a stage of disease when anything beyond ephemeral improvement was impossible. The patients who, under present conditions, are admitted to sanatoria come roughly into two groups: First. Patients with limited disease and little or no systemic disturbance. Comparatively few patients who now enter sanatoria come within this group. Second. Patients with more extensive or acute disease. In a large proportion of cases within the first group the immediate result of sanatorium treatment extending over three to six months is the complete restoration of general health and working capacity with arrest of disease. In a large further proportion of cases in the same group there is recovery of working capacity and apparent restoration of general health without complete arrest of disease. For patients coming within the second group a similar period of treatment in a sanatorium results: (_a_) In restoration of general health and working capacity with arrest of disease in only a small proportion of cases; (_b_) In recovery of working capacity and apparent restoration of general health without arrest of disease in a fair proportion of cases; and (_c_) In the remainder, disease progresses steadily with or without temporary improvement in general health. The subsequent history of sanatorium patients varies greatly. Some of them maintain their health indefinitely on return to their ordinary life. Others who have been discharged with arrested disease ultimately relapse, even if they live under excellent environmental conditions; and such relapses are excessive among those who return to unsatisfactory conditions of life and work. Among patients discharged from a sanatorium without arrest of the disease a small proportion ultimately recover completely, but the majority relapse at a date which is earlier or later in accordance more or less with the conditions under which they live and work and the severity of their disease. The experience of the last few years has been that only a small proportion of the patients admitted to sanatoria are cases in which arrest of the disease can be anticipated; and this will continue until the disease is more generally detected at an earlier stage than at present, and the sanatorium treatment is prescribed and continued solely in accord with the medical needs of the patient.