Branching Processes in Biology Motivating Examples and Other Preliminaries Biological Background The Galton Watson Process The Age Dependent Process: The Markov Case The Bellman Harris Process Multitype Processes Branching Processes with Infinitely Many Types References. This book provides a theoretical background of branching process and discusses their biological applications. Branching processes are a well developed and powerful set of tools in the field of applied probability. The range of applications considered includes molecular biology cellular biology human evolution and medicine. The branching processes discussed include Galton Watson Markov Bellman Harris Multitype and General Processes. As an aid to understanding specific examples two introductory chapters and two glossaries are included that provide background material in mathematics and in biology. The book will be of interest to scientists who work in quantitative modeling of biological systems particularly probabilists mathematical biologists biostatisticians cell biologists molecular biologists and bioinformaticians. The authors are a mathematician and cell biologist who have collaborated for more than a decade in the field of branching processes in biology.