Since the first report of a mutation in the tyrosinase gene that causes tyrosinase-negative oculocutaneous albinism (OCA), more than 25 alleles with a different mutation in patients with three types of OCA, i.e., tyrosinase-negative OCA (type IA), yellow-mutant OCA (type IB), and temperature sensitive OCA (type ITS), have been found in several laboratories. The mutated alleles are presently classified into three types. The first and the second group of alleles, termed t- and y, produce tyrosinases with no enzyme activity and with very low activity, respectively. The third, termed ts, produces temperature-sensitive tyrosinase with very low activity at 35 degrees C, but with no activity at temperatures greater than 35 degrees C. Various combinations of these alleles result in tyrosinase-negative (t-/t-), yellow mutant (y/y, y/t-, y/ts), or temperature-sensitive (ts/t-, ts/ts) OCA.