We investigate differences in patients’ length of stay between National Health Service (NHS) public hospitals, specialised public treatment centres and private treatment centres that provide elective (non-emergency) hip replacement to publicly funded patients. We find that the specialised public treatment centres and private treatment centres have, on average, respectively 18% and 40% shorter length of stay compared with NHS public hospitals, even after controlling for differences in age, gender, number and type of diagnoses, deprivation and regional variation. Therefore, we interpret such differences as because of efficiency as opposed to selection of less complex patients. Quantile regression suggests that the proportional differences between different provider types are larger at the higher conditional quantiles of length of stay. Copyright © 2012 John Wiley & Sons, Ltd.