The subject matter of this article, while largely statistical, has proved most instructive to us, and it is presented with the hope that the proverbial dryness of figures will be less arid in this instance, because of their importance. The material is based for the most part on data which we have collected in the preparation of the chapter on prognosis for the second edition of the monograph "Hypertrophy of the Prostate" by the senior author. In contrasting the chapter on prognosis in the previous edition of the work with the present one, an interval of fifteen years having elapsed, one is immediately impressed with the vagueness, the uncertainty and the misgivings with which prostatectomy was viewed only a comparatively few years ago. Then it was a procedure to be adopted only after palliative treatment had been tried unsuccessfully. It is not necessary to review the developmental steps in our