Single-pass DNA sequencing of cDNAs selected at random from a human mixed tissue cDNA library have generated a series of more than 2000 expressed sequence tags. One hundred twenty-eight unique cDNA fragments with little or no known protein or nucleic acid homologies have been selected for further analysis. Oligonucleotide primer pairs have been designed from the cDNAs and used in PCR amplification in combination with genomic DNA from a panel of monochromosomal somatic cell hybrids. This has allowed us to assign 70 of these transcribed genes to a single chromosome, and a further 9 have been located on two or three chromosomes. Additionally, 3 cDNAs contain short tandem repeats that may allow them to be further localized by linkage analysis.