Mental illness is a growing, and largely unaddressed, problem for the population and for emergency department (ED) patients in particular. Extensive literature outlines sex and gender differences in mental illness' epidemiology and risk and protective factors. Few studies, however, examined sex and gender differences in screening, diagnosis, and management of mental illness in the ED setting. Our consensus group used the nominal group technique to outline major gaps in knowledge and research priorities for these areas, including the influence of violence and other risk factors on the course of mental illness for ED patients. Our consensus group urges the pursuit of this research in general and conscious use of a gender lens when conducting, analyzing, and authoring future ED-based investigations of mental illness.