A series of 195 random chromosome 22-specific probes, equivalent to approximately 1% of the size of this chromosome, have been isolated from a chromosome 22-specific bacteriophage lambda genomic library. These probes were mapped to four different regions of chromosome 22 on a panel of five somatic cell hybrids. Restriction fragment length polymorphisms were detected by 28 of the probes mapping to 22q12-qter. Evolutionarily conserved sequences in human, mouse, and Chinese hamster DNA were detected by 12% of the isolated probes.