Reaction rate constant plays an essential role in understanding a wide range of processes in chemistry, biochemistry and physics, and thus it is very intuitive for researchers to have a first look at the rate constant of a chemical reaction. This book describes the recent efforts on rate constant computations for reactions in gas phase, solutions and solid-state, covering those on developing new theories, modifying and improving the previously established ones, evaluating the quality of various kinds of theories, mechanistic analyses with rate constant computation, recent interest and the hottest issues in the area. An essential read for all chemists, physicists, biochemists working in the field.