One of the most puzzling and striking features of many of the genetically­ determined progressive neuromuscular diseases such as the spinal muscular atrophies and the muscular dystrophies is that muscular wasting and weak­ ness in these cases is curiously selective, at least in the early stages, pick­ ing out certain skeletal muscles and sparing others. The diagnosis of these conditions has largely depended in the past upon the recognition of specific patterns of involvement of individual muscles and muscle groups, taken along with information derived from the mode of inheritance within the in­ dividual family and the results of special investigations. The investigations of most value have proved to be serum enzyme studies, electromyography and related techniques, and muscle biopsy. The advent of CT scanning has, however, introduced a new dimension; as the authors of this interesting monograph have clearly demonstrated, it is now possible, using the whole­ body scanner, to define patterns of muscular atrophy in the limbs and trunk much more precisely than by any other method. Not only does this techni­ que demonstrate which muscles are involved, but the changes in relative density provide useful information about the severity of the process and about the progress of the disease if the studies are performed serially. This monograph is pleasantly written and most attractively illustrated.