Book excerpt: Transformations using enzymes have been extensively investigated in the last two decades and the results promise great potential for this growing field, especially in the area of synthetic organic chemistry mainly due to of its many advantages. Accordingly, this book has attempted to bring out the advantages of using enzymes involving complex underivatized and unprotected substrates in non-polar media under homogenous and heterogeneous reaction conditions. Merits and demerits of using enzymes in terms of yields and selectivity/specificity are presented without any prejudice. Almost all the reactions dealt with are from the author’s laboratory comprising diverse substrates, and the catalysis involves two important hydrolyzing enzymes, extensively examined for the reverse reactions. Thus, esterification involving lipses and glycosylation involving glycosidases were investigated with respect to various strategies like optimization of reaction conditions, response surface methodology and kinetics, carrying out reactions under solvent, non-solvent and super critical carbon dioxide conditions. In short, the work presented is to ensure the comprehension of the problems faced by the researchers in this area so as to work out further efficient strategies for carrying out enzymatic transformations in the laboratory successfully with better yields and specificity.