To examine whether renal cell carcinoma displays altered CD44 expression we performed reverse transcription-polymerase chain reaction (RT-PCR) analysis of CD44 in 38 specimens from renal cancer, normal kidney and metastases of 19 patients and 6 renal cancer cell lines. To detect the CD44 variants, we utilized the RT-PCR Southern blot method. One out of 19 (5.3%) renal cancer specimens expressed a larger molecular weight band than 1 kb by RT-PCR analysis, in contrast to previous findings in colon and breast cancer. The band patterns in RT-PCR were different in 14/17 (82.4%) cases between normal kidney and tumors, and a band of about 700 bp was especially marked in 12/17 (70.6%) tumor specimens and 4/6 (66.7%) cell lines. By cloning and sequencing of the 700 bp band, we found that this variant is identical to the CD44 variant sharing only exon v10. Examination by Northern blot analysis has revealed that all tumors express a higher level of CD44 mRNA than paired normal kidneys. These findings suggested that the CD44 variants sharing exon v10 play some role in renal cancer.