Tyrosinase is an important enzyme in the formation of pigment throughout the animal kingdom and many assays have been described for measuring its activity. This paper describes an assay which has been optimized to measure the enzymatic activity of mammalian tyrosinase and describes the procedures from which the optimum conditions were determined. The preparation and storage of the stock reagents required to perform the assay are also described in detail as well as some discussion pertaining to the preparation of samples prior to assay.