The cause of hearing loss after spinal anaesthesia is unknown. Up until now, the only factor studied has been the effect of the diameter of the spinal needle on post-operative sensorineural hearing loss. The aim of this study was to describe this hearing loss and to investigate other factors influencing the degree of hearing loss. Two groups of 22 similar patients were studied: one group received 6 mL prilocaine 2%; and the other received 3 mL bupivacaine 0.5%. Patients given prilocaine were more likely to develop hearing loss (10 out of 22) than those given bupivacaine (4 out of 22) (P<0.05). The average hearing loss for speech frequencies was about 10 dB after prilocaine and 15 dB after bupivacaine. None of the patients complained of subjective hearing loss. Long-term follow-up of the patients was not possible.