We have previously identified a partial human cDNA for MAP2, and we now report the isolation of human cDNA clones for tau. The RNA species recognized by the tau clones is a 6 kilobase (kb) message that is expressed in the human brain but not in other human tissues, and exhibits a developmental shift in size. We also report the human chromosomal localization of the MAP2 and tau genes. The MAP2 cDNA pKN7 was used to localize the MAP2 gene to chromosome 2q34-35. The tau cDNAs were used to confirm the presence of a tau gene on chromosome 17q21 and an additional region of homology on chromosome 6p21.