Background: We have recently reported that connexin (Cx) 32 is down-regulated in a human renal cell carcinoma (RCC) cell (Caki-2 cell). Hypothesis: We postulated that the down-regulation of Cx32 gene in the RCC cell is due to hypermethylation of its promoter region. Methods: We estimated methylation status in the promoter region of Cx32 gene in the RCC cell by DNA digestion with methylation-sensitive restriction enzyme and PCR, and methylation-specific PCR (MSP). We also checked the recovery of Cx32 gene expression in the RCC cell treated with a DNA methyltranferase inhibitor, 5-Aza-2’-deoxycytidine (5-Aza-CdR). Results: Treatment with 5-Aza-CdR resulted in induction of Cx32 expression in the RCC cell. Hypermethylation of the Cx32 promoter region in the RCC cell was confirmed by DNA digestion with methylation-sensitive restriction enzyme and PCR, and MSP. Conclusion: We suggest that hypermethylation in the promoter region is a mechanism for the Cx32 gene repression in the RCC cell.