Much has happened in the field of mechanistic enzymology in the past 15 to 20 years, but books dealing with the mechanisms of enzymatic reactions were written a generation ago and have not been updated. There is no longer a single volume or a small collection of volumes from which students can obtain a clear understanding of the state of knowledge regarding the chemical mechanisms by which enzymes catalyze biological reactions. There is no single volume on enzymatic mechanisms to which medicinal chemists and biotechnologists can refer. As the modern day replacement for C.T. Walshs classic 1979 book on the subject, Frey and Hegemans text promises to be an instant success.