A case is reported in which a patient with the typical clinical and pathologic features of Letterer‐Siwe disease survived more than 15 years from the onset of symptoms. A search of the literature revealed only four other instances of similarly long survivals. An attempt to correlate clinical features and treatment data with length of survival in 96 adequately documented cases collected from the literature showed few clear‐cut trends. Lack of pulmonary involvement and the absence of thrombocytopenia seem to be of favorable prognostic significance. Of the patients 18.9% survived 2 years or longer; all but one of these were still alive at the time of the last follow‐up. Survivals of 2 years or longer were significantly higher in patients who had received corticosteroids than in those who had not. The number of reported long‐term survivals is too small to permit one to detect a common denominator that would make it possible to predict such a favorable clinical course.