Arginase hydrolyzes the guanidine group of arginine, converting it to ornithine and urea.  This hydrolysis involves an oxygen nucleophile that is flanked by two manganese ions, and regulates the supply of arginine.  Arginine is required for NO biosynthesis, and inhibitors of arginase are therefore potential pharmaceutical agents.  Some of the best inhibitors of arginase are transition state analogs.  We have therefore investigated the use of silanediols as potential inhibitors of this enzyme.  These are the most sterically unencumbered silanediol enzyme inhibitors prepared to date.  Their synthesis and properties will be described.