In addition to performing its prime function as a vehicle for scientific communications of varied colora- tions, Molecular and Cellular Biochemistry is again focusing on two subjects which it treats in depth. One of these is a book issue dealing with the transglutaminase reaction. The other is this issue that deals with induction and modulation of enzymes. This is a very broad subject that calls for broader coverage than could be included in one book issue. However, I have elected to include only certain contributions that serve as general examples of the principles involved. There are six articles on enzyme regulation in hepatocyte culture. These include arginase and argino-succi- nate synthetase, y-glutamyl transferase and plasminogen activitor. Other regulatory enzymes that are discussed are protein kinases, 2,3-bisphosphoglycerate synthetases, carbamoyl phosphate synthetase, heme oxygenase, cytochrome P-450, tyrosine hydroxylase, fatty acid synthetase, acetyl eoA carboxylase, among others. Also included is the regulation of several enzyme messengers RNAs. As in the past, subscribers to the journal will receive this double volume as a continuation of regular issues of the journal Molecular and Cellular Biochemistry. This double volume will also be available separately in the form of a book issue to interested readers through Martinus Nijhoff Publishers. v.A. Najjar Part I Molecular and Cellular Biochemistry 53;54,11-21 (1983). (c) 1983, Martinus 1\ ij hoff Publishers. Boston. Printed in The Netherlands.