We describe 2 cases of renal cell carcinoma arising in acquired cystic disease of the kidney (ACDK) in patients with end-stage renal disease undergoing hemodialysis for more than 5 years and provide a brief review of the complications of ACDK. In both cases, abundant calcium oxalate crystals were observed within the tumors. Histologically, one of the tumors was a conventional (clear cell) renal cell carcinoma. The other tumor was a bilateral papillary renal cell carcinoma. Both tumors were high-grade carcinomas with extensive oncocytic (acidophilic) features. Also noted within the kidneys were cysts with atypical papillary hyperplasia. The clinicopathologic findings along with review of the literature suggest a relationship between tumor growth and calcium oxalate crystal deposition in patients undergoing hemodialysis with ACDK.