Following two deaths from respiratory failure secondary to opioid toxicity in patients admitted for surgical repair of fractured neck of femur, we retrospectively studied the serum urea and electrolyte concentrations of 1511 consecutive patients requiring surgery for proximal femoral fracture, and calculated their glomerular filtration rate. Five hundred and forty-five (36.1%) patients had renal dysfunction on admission (glomerular filtration rate < 60 ml x min(-1).1.73 m(-2)); 435 (28.8%) had grade 3 chronic kidney disease (moderate; glomerular filtration rate 30-59 ml x min(-1).1.73 m(-2)), 82 (5.4%) had grade 4 disease (severe; glomerular filtration rate 15-29 ml x min(-1).1.73 m(-2)) and 28 (1.9%) had grade 5 (renal failure; glomerular filtration rate < 15 ml min(-1).1.73 m(-2)). The 30-day mortality for patients with renal dysfunction (62/536; 11.6%) was significantly greater (p = 0.004) than for patients with normal renal function (68/958; 7.1%), although median (IQR [range]) postoperative lengths of stay were similar 15 (10-22 [1-125]) vs 14 (9-22 [1-120]) days respectively; p = 0.06). Renal impairment is common in patients admitted for fixation of fractured neck of femur, who are consequently at risk of opioid toxicity.