The first mutant tan streak deer mice appeared in the initial laboratory-bred generation of a stock of Peromyscus maniculatus nubiterrae collected in Macon County, North Carolina. Laboratory progeny from the original animals were bred and mated among themselves and to wild-type individuals. The tan streak phenotype is characterized by nearly complete absence of coat pigmentation, except for a pale tan patch or narrow stripe extending mid-dorsally posteriorly from the head. The band is frequently somewhat broader in the shoulder region, occasionally forming a cross-shaped pattern. There is no evidence of black eumelanin in any part of the coat. The eyes are fully pigmented, appearing black, and pigment is present in the skin of the ears and elsewhere. The trait is inherited as an autosomal recessive. The genetic locus is provisionally designated tns. Crosses between homozygous tan streak (tns/tns) animals and albino (c/c), ivory (i/i), non-agouti (a/a) and brown (b/b) deer mice produced only wild-type progeny, indicating that the tns mutation is not at any of these loci.