Certain pertinent history of the recent development in the field of power generation is given in graphic form. The problem of rehabilitation of steam power plants is shown to arise from the great rapidity of this development. While no simple rule can be given to indicate when, if at all, rehabilitation ts justifiable, certain guiding criteria which may serve as aids in analysis are stated. These are followed by brief accounts of the various methods available for rehabilitating plants to different extents. Finally, it is suggested that the possibility of later rehabilitation be taken into account when designing plants for systems in which history or argument indicate that such action is to be expected.