A case history is reported here in which leukocytosis, thrombocytosis and hypercalcemia associated with rapidly relapsing squamous cell carcinoma (SCC) of the renal pelvis were observed. In a 58-year-old man, SCC of the renal pelvis was documented during nephrolithotomy, and right nephrectomy was performed. Local relapse of the tumor occurred rapidly in 2 months' time and hypercalcemia, leukocytosis and thrombocytosis worsened in accordance with tumor volume. Cranial computerized tomography (CT), thorax CT and bone scintigraphy were negative for metastasis. The serum parathyroid hormone level was 28 pg/ml (normal 9-55 pg/ml). To disclose leukocytosis and thrombocytosis, peripheral smear and bone marrow aspiration were performed and no pathologic finding regarding any hematologic disorder was found; the samples were also BCR-ABL negative and Philadelphia chromosome negative. Production of several factors by tumor cells may be responsible for this paraneoplastic syndrome. The association of SCC of the renal pelvis with this triple paraneoplastic syndrome is an extremely rare occurrence. Copyright (C) 2001 S. Karger AG, Basel.