Cell proliferation is an increase in the number of cells as a result of cell growth and cell division. A series of growth disorders can occur at the cellular level, often causing cancer. This book examines and discusses recent developments in this field. In particular, the changes that occur in cell viability, cell proliferation and cytotoxicity following therapy and laser irradiation are studied. Furthermore, the effects that probiotic bacteria and gastrointestinal mucosa have on cell proliferation are looked at. Data from literature suggests a possible use for probiotics in the therapeutic management of different diseases. This book reviews the ways to estimate cell proliferation and a general view about the principal methods used to evaluate cell populations kinetics are given. Also, research has shown that reductions in cell proliferation by nutrition interventions may indicate a decrease in cancer risk. Thus, this book examines the ability of dietary restriction regiments to reduce cell proliferation rates and cancer risks in humans and animals.