A safety behaviour is an overt or covert strategy employed in order to prevent a feared outcome from occurring. These behaviours can, however, prevent the disconfirmation of unhelpful beliefs, and may make the feared outcome more likely to occur (Salkovskis, 1991). The current study extends Harvey's (2002a) investigation of safety behaviours in insomnia by developing a questionnaire measure designed to assess the use of safety behaviours that are employed to promote sleep and cope with tiredness. A development sample of 132 individuals with and without insomnia was employed to develop the 32-item Sleep-Related Behaviours Questionnaire (SRBQ). The SRBQ showed good internal consistency and was able to discriminate normal sleepers from those with insomnia. Interestingly, most safety behaviours were associated with impairment in both sleep and daytime functioning. This highlights that day- and night-time processes may be interlinked in insomnia, and stresses the importance of research and treatment focusing on both the day and night. Future research is needed to further investigate the psychometric properties of the SRBQ, and to explore the relationships between safety behaviours and dysfunctional beliefs about sleep.