Objective. The objective of this Group for Research and Assessment of Psoriasis and Psoriatic Arthritis (GRAPPA) initiative is to develop a questionnaire to determine the presence of a flare of disease activity in psoriatic disease (PsD), for use in clinical care and research settings. Methods. In 2014 and 2015, 2 online Delphi surveys of patients and physicians attempted to achieve consensus about items that might discriminate a flare of disease. In the first round, items were derived from previous qualitative studies with patients; in the second round, new items, suggested by both patients and physicians, were added. Survey results were discussed at the 2015 GRAPPA annual meeting, and 8 breakout groups discussed specific aspects of PsD flares. Results. Survey participants were patients (n = 103 and n = 57 in rounds 1 and 2) and physicians (n = 125 and n = 81). Items for flare covered 6 domains (joints, skin, emotion, participation, fatigue, and unclassified). Patients agreed that 20 items were important (10 joints, 1 participation, 8 fatigue, 1 unclassified), and physicians agreed on 23 items (5 skin, 11 joints, 4 participation, 3 unclassified). Eight items were selected as important by both groups: 7 joint items and 1 unclassified. Patients emphasized fatigue and physicians emphasized skin and participation. Breakout groups concluded that the components of a flare instrument should be derived from patients. A flare should be defined as a change in disease state requiring intervention. Conclusion. The concept of flare in PsD covers articular, skin, emotional, participation, and fatigue domains. Further work is required to specify items that represent these domains.