Optical head-mounted displays (OHMDs) could support members of emergency medical services in responding to and managing mass casualty incidents. In this contribution, the authors describe the human-centered design of two applications for supporting the triage process as well as the identification of hazardous materials. They were evaluated with members of emergency medical services and civil protection units. In this regard, challenges and approaches to human-computer interaction with OHMDs in crisis response and management are discussed. The conclusion is drawn that often mentioned advantages of OHMDs like hands-free interaction alone will not lead to usable solutions for safety-critical domains. Interaction design needs to be carefully considered right down to the last detail.