Haematological and infectious toxicity was correlated to renal function in 272 newly diagnosed myeloma patients given standard dose melphalan–prednisone (MP) as initial treatment without dose adjustment for renal impairment. The glomerular filtration rate (GFR) was estimated by calculated creatinine clearance. Haematological toxicity was found to be significantly related to renal dysfunction. Haematological toxicity World Health Organization (WHO) grades 3–4 after the first MP course was seen in 18%, 28% and 36% of patients with a creatinine clearance of >50, 30–50 and <30 ml/min respectively. WHO grades 3–4 infections occurred in 6% and were not significantly related to renal function. We conclude that MP therapy can be used for initial therapy in myeloma patients with renal impairment but suggest that reduction of the melphalan dose should be considered in patients with a GFR of <30 ml/min. As only 2% of our patients had a clearance of ≤10 ml/min no conclusions can be drawn for this subgroup.