The eighteenth series of the British medical drama television series Casualty began airing on BBC One in the United Kingdom on 13 September 2003, and concluded on 28 August 2004. The series consists of 46 episodes, which focus on the professional and personal lives of medical and ancillary staff at the emergency department (ED) of the fictional Holby City Hospital. Foz Allen serves as the series producer, while Mal Young and Mervyn Watson act as the executive producers of the series. Twelve regular cast members reprised their roles from the previous series and six actors joined the cast during the series. Original cast member Julia Watson, who portrays Baz Wilder, also returned.