We are pleased to present this second volume of a series that has already received much interest. The application of magnetic resonance methods to the study of actual biological systems as contrasted to cell-free samples, although not entirely novel, as demonstrated by Civan and Shporer in Volume I, has taken on new dimensions with the use of phosphorus-31 and carbon-13 NMR in studying cells, tissues, and organelles. The applications of 31 P NMR to such systems is reviewed in this volume, while carbon-13 will be covered in a later one. The use of nitroxide spin labels has grown to the point...