The gene for the granulocyte colony-stimulating factor (G-CSF) receptor (CSF3R) was localized on the p35-p34.3 region of human chromosome 1 by in situ hybridization using human G-CSF receptor cDNA as the probe. Polymerase chain reaction using oligonucleotides specific for the human CSF3R produced a specifically amplified DNA fragment with DNA from mouse A9 cells that contained human chromosome 1 but not other human chromosomes. Localization of the CSF3R on chromosome 1 was further confirmed by the spot-blot hybridization of sorted human chromosomes.