Renal Cell Carcinoma (RCC) has been associated with the loss of heterozygosity at several loci on the short arm of chromosome 3 (3p). We have previously found that one of these loci, D3F15S2 (pH3H2) was lost in 76% of the tumor cells derived from heterozygous donors (Kovacs, G., Erlandsson, R., Boldog, F., Ingvarrsson, S., Müller-Brechlin, R., Klein, G. & Sümegi, J. (1988), Proc. Natl. Acad. Sci., 85, 1571-5). More recently we have identified a putative CpG island in the vicinity of D3F15S2, suggesting that DNA sequences in or around this site may have coding potential (Boldog, F., Erlandsson, R., Klein, G. & Sümegi, J. (1989). Cancer Genet. Cytogenet., 42, 295-306). The screening of a human placenta cDNA library with DNA probes derived from D3F15S2 has led to the isolation of several cDNA clones. They identified a 2.9 Kb long message in human placenta and kidney. In total RNA from 11 of 15 primary RCCs the gene expression was reduced to less than 20% compared to eight normal kidneys. This low level of expression may be due to contaminating normal tissue. In the remaining 4 tumors the expression varied from 24-51% compared to normal kidney. To facilitate reference, the gene was provisionally designated as 'RIK'. It was expressed in the HEK 293, one osteosarcoma (HOS), two carcinoma (COLO320 and QDMT), and three Burkitt lymphoma lines (BL2, BL29 and BL31). It was not expressed in one Burkitt lymphoma (DG75) and two EBV transformed lymphoblastoid cell lines (LCL) (NAD-20 and Cherry).