This book presents an overview of the most relevant protein knockdown techniques. Readers will find a description of the generation and use of recombinant human antibodies, ER intrabodies and peptides as well as a description of the working mechanism and potential of the inhibitory action of each of these molecules. The book will also describe the selection and activity of a number of phosphatases, aptamers and allosteric modulators, focusing on A G protein coupled receptors. The book starts with a chapter on the in silico prediction of target-inhibitor interactions. Key aspects of this book are: - Selection strategies for monoclonal and recombinant human antibodies - Selection strategies for ER intrabodies, peptides and aptamers- Examples of the most efficient inhibitors and their applications in protein biochemistry and cell biology - Antibodies for cancer therapy and inhibitors of angiogenesis. The book will be of great interest to scientists and students working in the life sciences on all areas related to protein biology. The variety of methods to modulate the activities of specific proteins which are introduced here will be of great benefit to the reader who is interested in general protein research or to readers who have very specific protein related questions.