The present volume contains the edited transcript of a Totts Gap Colloquium held May 19-21, 1980 sponsored by the Muscular Dystrophy Association. The aim of the colloquium was to bring into focus data relating to cell membranes that might contribute to understanding the pathogenic mechanism of Duchenne muscular dystrophy. A major impediment to progress in understanding the patho- genesis of muscular dystrophy has been the failure, so far, to identify the basic genetic defect. Pending the identification of the genetic lesion in Duchenne dystrophy and, in view of scattered but persistent indications of a basic membrane disturbance, it seemed worthwhile to explore in open dialogue the current state of knowledge of membrane morphology and chemistry with an eye to possible leads for further investigation. The participants, drawn from a variety of interested disciplines, attempted to synthesize and reconcile their findings and to identify crucial areas of ignorance in need of exploration. For the most part they avoided specialized jargon and spoke in a language that could be understood by the rest of the group. Apart from providing a review of widely varying approaches to the study of the composition and behavior of cell membranes, the discussions brought together current think~g on strategies and approaches to the study of the pathogenesis of muscular dystrophy. Already the personal contacts made at the colloquium have led to new inter-institutional collabora- tive investigations.