Judging from the articles published in Biochemistry, magnetic resonance techniques (NMR and ESR) are now among the most popular methods in biochemical research. The series Biological Magnetic Resonance, the fifth volume of which we are proudly presenting, is intended to provide authori­ tative coverage of topics of current interest. Previous volumes have covered a number of aspects in a thorough and pedagogical fashion rarely found in other publications in this field. Continuing to fulfill the mission of the series, this volume presents a chapter by Baxter, Mackenzie, and Scott on the applications of carbon-13 NMR spectroscopy in investigations of methabolic pathways in vivo. Blom­ berg and Ruterjans give a comprehensive summary of the use of nitrogen-15 NMR in studies of systems of biological interest. Phosphorus-3I NMR investigations of enzyme systems are described by Rao. Tsai and Bruzik outline the principles of and summarize the state-of-the-art advances in the 18 use of oxygen isotopes e 70 and 0) in phosphorus-3I and oxygen-17 NMR studies of biophosphates. Lipid-protein interactions as reflected in ESR and NMR data are discussed by Devaux. We wish to thank the authors for their cooperation in maintaining the and continued high standards of the series.