The authors report 5 cases of polycythaemia associated with renal cancer. This paraneoplastic syndrome is present in less than 5% of all renal cancers. It is considered to be a factor of poor prognosis, as it is often associated with metastatic and/or high-grade cancer Polycythaemia, secondary to secretion of erythropoietin (EPO) by the tumour, is reversible after nephrectomy. The persistence or recurrence of polycythaemia after nephrectomy may indicate incomplete local resection or the presence of EPO-secreting metastases.