Background: More elderly patients are being treated with chemotherapy. Reliable and accurate measures of renal function are needed to obtain predictable, safe and effective exposure to renally excreted drugs. The Jelliffe, Cockroft-Gault and Wright formulae have been used to evaluate renal function, although they have not been validated in elderly oncology patients. We performed a retrospective evaluation of these formulae using the [Cr-51]-ethylenediamine tetraacetic acid ([Cr-51]-EDTA) method of measuring glomerular filtration rate (GFR) as the 'gold standard'. Patients and methods: Inclusion criteria were age greater than or equal to70 years and serum creatinine 50 ml/min. These results allow the physician to make a decision regarding the use of the formula based on an expected degree of bias.