The five human CC-chemokine receptors functionally characterized to date were mapped by using a radiation hybrid panel and YAC contigs. The genes encoding CC-CKR1, CC-CKR2, CC-CKR3, and CC-CKR5 (designated respectively CMKBR1, CMKBR2, CMKBR3, and CMKBR5 in the Genome Data Bank) were found to be clustered in the 3p21.3 region of chromosome 3, between the AFM362WB9 and the WI-6983 markers. The four genes fall within a total distance of about 350 kb. The fifth gene (CMKBR4, encoding the CC-CKR4 receptor) was located more distally (3p24) on the same chromosome, between the FB18G7 and the D3S1768 markers. These localizations were confirmed by mapping the genes into the YAC contigs covering these regions. The clustering of chemokine receptor genes suggests a relatively recent expansion of the gene family by gene duplication. Deletions and duplications of the 3p21 region have been described in neoplastic disorders of the hematopoietic lineage, suggesting a potential link with the CC-chemokine receptor gene family.