We used microarrays to examine individual-based differences in gene expression in primary cultures of renal tubular cells derived from Japanese subjects. The subjects had solitary tumors in the kidney or urinary tract, which were diagnosed pathologically as renal cell carcinoma or transitional cell carcinoma. Renal tissue samples collected from a non-tumorous portion of the tissue were regarded as normal tissues, as there were no abnormal microscopic findings and no evidence of renal dysfunction from the clinical laboratory data. The genome-wide gene expression profiles of nine human renal cell cultures were analyzed using the Affymetrix GeneChip HG-U133A and HG-U133B arrays. Approximately 8, 500 transcripts exhibited significant differential expression (p < 0.05) among the subjects, and the coefficients of variation for 1, 338 transcripts were greater than 50%. Some of these transcripts encode drug-metabolizing enzymes (e.g., UGT1A8 and UGT1A9) or sodium/phosphate cotransporters (e.g., PDZK1). These data provide the basis for toxicogenomic studies using primary cultured renal cortical cells from Japanese subjects.