Much of the recent spectacular progress in the biological sciences can be at­ tributed ot the ability to isolate, analyze, and structurally characterize proteins and peptides which are present in cells and cellular organelles in only very small amounts. Recent advances in protein chemistry and in particular the application of new micromethods have led to fruitful advances in the understanding of basic cellular processes. Areas where protein-chemical studies have resulted in interest­ ing discoveries include the peptide hormones and their release factors, growth factors and oncogenes, bioenergetics, proton pumps and ion pumps and chan­ nels, topogenesis and protein secretion, molecular virology and immunology, membrane protein analysis, and receptor research. In fact, the key methods are now on hand to unravel many of the major outstanding problems of molecular biology and in particular questions of fundamental interest which relate to devel­ opmental biology and specificity in cell-cell interaction. In this volume we have assembled descriptions of procedures which have re­ cently been shown to be efficaceous for the isolation, purification, and chemical characterization of proteins and peptides that are only available in minute amounts. Emphasis is placed on well-established micromethods which have been tested and found useful in many laboratories by experienced investigators. The chapters are written by specialists, and describe a range of sensitive techniques which can be used by researchers working in laboratories with only modest resources and equipment.