As constituents with potential contact allergenic and toxic properties in crude Ginkgo extracts a group of alkylphenols (e.g., ginkgolic acids, ginkgol, bilobol) has been de- scribed. Thus, for reasons of drug safety a maximal concentration (≤ 5 ppm) of ginkgolic acids is requested by the Monograph of the Commission E of the former German Federal Health Agency (Bundesgesundheitsamt, BGA). During production of the standardized Ginkgo extract EGb 761, alkylphenols are largely eliminated as water insoluble compounds (decanter sludge) from the pri-mary acetone extract.