Both squamous cell carcinoma and carcinosarcoma of the renal pelvis are uncommon. We report on two cases, one carcinosarcoma and one squamous cell carcinoma of the renal pelvis. In the patient with squamous cell carcinoma of the left kidney, the tumor was neither detectable on preoperative radiological evaluation nor grossly visible in the surgical specimen. This patient, a 56-year-old man, presented with left lumbar pain, hematuria, fever, 4-5 kg weight loss, and untreated nephrolithiasis of the left kidney that had been diagnosed 20 years earlier. The second patient, an 87-year-old woman, also had a long history of left kidney nephrolithiasis and presented with left lumbar pain and hematuria. Both patients underwent nephrectomy for removal of the non-functioning hydronephrotic left kidney. In both cases, microscopic examination of the surgical specimen revealed squamous metaplasia and dysplasia in the pelvicalyceal mucosa, and islands of atypical squamous cells in the renal parenchyma. In the second case, the kidney also showed sarcomatous changes in the pelvis.