Fungi are of considerable interest and economic importance to our society. They provide us with organic acids (such as citric, itaconic, fumaric, lactic or malic) which are used in food industry and as raw materials in chemical syntheses. They yield products which have striking pharmacological properties such as ergot and other indole and quinoline alkaloids (ergocristine, lysergic acid amide, psilocybin, viridicatin), gibberellins and hormones (antheridiol, zearalenone, trisporic acids). Although some of them produce mycotoxins of which luteoskyrin and aflatoxins are carcinogenic, they also elaborate life-saving penicillins and cephalosporins. Fungi have been used in the preparation of Oriental foods and condiments such as koji, shoyu (soy sauce), miso, sufu (Chinese cheese), tempeh or food-coloring matter known as ang-kak (Hesseltine, 1965; Hesseltine and Wang, 1970) and edible mushrooms (Hayes, 1974). In addition to these properties, fungi carry out simple reactions which can be defined in precise chemical terms. Since some such reactions can be performed more economically by microbial rather than a strictly chemical manipulation, fungal steps have been incorporated into large-scale processes which yield valuable medicinals such as steroid hormones, semisynthetic penicillins and cephalosporins. On the laboratory scale, they have been employed to study synthetic, structural, stereochemical and kinetic problems of organic chemistry. Several features make fungal-and microbial transformations in general-particularly attractive for this purpose. The reactions are mediated by enzymes which are chiral catalysts with rigid substrate-binding characteristics and usually display high reaction specificity. Thus they will catalyze reactions of only one or two virtually equivalent groups of the substrate molecule without the need of protecting other groups in a way used in the synthetic organic chemistry. They allow the chemist to functionalize only specified non-activated carbon atoms, to introduce centers of chirality into an optically inactive molecule, to reduce ketones of varying structures to the corresponding alcohols with a high degree of stereospecificity and predictability (Prelog, 1960), to resolve racemic mixtures or to carry out reactions on substrates which are sensitive to heat or pH. Furthermore, one enzymatic step may replace several chemical steps and thus make the overall process more efficient and economical (Perlman, 1976; Sih and Rosazza, 1976). OUTLINE OF METHODS AND APPROACHES