Tyrosinase is the key enzyme for melanin,synthesis in mammalian melanocytes and has been considered to be a unique marker for the study of melanocyte differentiation. A cDNA library was constructed from poly(A)+ mRNA from mouse melanocytes and screened using anti- tyrosinase antiserum and oligonucleotide probes corresponding to amino acid sequence of tyrosinase. sequencing of some cDNA clones positive in these screenings gave a nucleotide sequence of 1838 nucleotides including a open reading frame of 1344 nucleotides that was found to correspond exactly to the amino acid sequence of the cyanogen bromide fragments of tyrosinase.