The first stage of the Royal College of Anaesthetists Third National Audit Project to assess the incidence of major complications of central neuraxial block in the UK was a 2-week national census of block use. A reporting system was established in the 309 National Health Service hospitals believed to undertake surgical work and data were received from 304, a response rate of 98.7%. Over 90% of these were judged by the reporters to be 'accurate'. The total number of procedures reported as being performed in the 2-week period was 27,533: extrapolation using a multiplier of 25 suggests that nearly 700,000 major blocks are performed annually (315,000 spinals, 287,000 cervical, thoracic or lumbar epidurals, 42,000 combined spinal-epidurals and 56,000 caudal epidurals). After the second stage of the project, which will record complications from the same hospitals over a 12-month period, these data will be used as denominators to calculate the incidences of complications.