Suicide is a leading cause of death in young people aged 15-29 globally (World Health Organization, 2018), making it a major public health concern. Despite extensive research on suicide risk factors, scientists are still unable to reliably predict when someone with suicidal ideation (SI) will make a suicide attempt (May & Klonsky, 2016, Franklin et al., 2017). Further, while SI is relatively prevalent, many individuals who ideate do not go on to make attempts (Nock et al., 2008). SI and its risk factors vary significantly from day to day in people with a history of SI and suicide attempts (Kleiman et al., 2017). This underscores the importance of understanding the individual’s response to their SI, how their responses influence the ebb and flow of SI, as well as the transition from SI to suicide attempt. At present, the cognitive and behavioral responses to SI are not well understood or measured. Young people with a history of SI have reported low-to-moderate self-efficacy for coping during a suicide crisis (Czyz et al., 2016). Further, evidence suggests that young people who have lower scores on cognitive flexibility and social problem-solving ability are more likely to be at greater suicide risk (Chu et al., 2018; Miranda et al., 2012). These cognitive vulnerabilities and coping behaviours have not been fully elucidated. Existing coping scales (e.g. COPE inventory; Carver, 2013) and suicide resilience scales (e.g. Reasons for Living Inventory; Linehan et al., 1983, Suicide resilience inventory; Osman et al. 2004) lack items that delineate responses specific to SI. Therefore, the proposed project aims to develop a Response to Suicide Ideation Inventory (RSII), a self-report scale that quantifies how young people with a history of SI respond behaviorally and cognitively to their suicidal thoughts in their daily lives. The project will be undertaken in three phases. In the first phase, candidate items will be generated by drawing information from literature reviews, online communities, and suicide prevention resources. In the second phase, candidate items will be reviewed in consultation with other suicide researchers. 100 participants (aged 18 to 29, with a history of suicidal ideation in the past year) will also be recruited via an online data collection platform (e.g. Qualtrics) to pilot the RSII. A preliminary statistical evaluation of items will be conducted. The RSII will be revised according to the findings and feedback. In the final phase, the RSII will be distributed to a separate sample of 400 young people (same inclusion criteria and recruitment method as in the second phase). The initial psychometric characteristics of the RSII will be determined and recommendations for further development and potential use will be discussed.