The thirteenth series of the British medical drama television series Casualty commenced airing in the United Kingdom on BBC One on 5 September 1998 and finished on 13 March 1999. It saw another increase, this time to 28 episodes (the first two episodes aired on consecutive nights), including a feature-length Christmas episode. The series also acted as a launchpad for characters and storylines in the spin-off series Holby City, which started in January 1999.