In the succeeding pages the authors have collated scattered information about individual sulfatases and have endeavoured to indicate their physiological roles within the microorganism, the ways in which their synthesis is subject to genetic and physiological control, and their participation in natural processes such as the recycling sulfur. The authors have also attempted, for the first time, to discuss at length the mechanisms of action of some of the enzymes in relation to current knowledge about the nonenzymic hydrolysis of various types of sulfate ester. Although primarily directed towards those people interested in biochemistry and enzymology of microorganisms, it is the authors belief that there will be much in the book that will be of interest to worker in the mammalian field.