OBJECTIVE: To describe the qualitative process used to develop attributes and attribute levels for inclusion in a discrete choice experiments (DCE) for older adult physical activity interventions. DESIGN: Five focus groups (n=41) were conducted, grounded in the Health Action Process Approach framework. Discussion emphasized identification and prioritization attributes for a DCE on physical activity. Semi-structured interviews (n=6) investigated attribute levels and lay-language for the DCE. A focus group with physical activity researchers and health care providers was the final stakeholder group used to establish a comprehensive approach for the generation of attributes and levels. A DCE pilot test (n=8) was then conducted with individuals of the target patient population. All transcripts were analyzed using a constant comparative approach. SETTING: General community and university-based research setting. PARTICIPANTS: Volunteers (N=55) aged >45 years with knee pain, aches, or stiffness for at least 1 month over the previous 12 months. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Interview guides, attributes, attribute levels, and discrete choice experiment. RESULTS: The most influential identified attributes for physical activity were time, effort, cost, convenience, enjoyment, and health benefits. Each attribute had 3 levels that were understandable in the pilot test of the DCE. CONCLUSIONS: The identification of 6 physical activity attributes that are most salient to adults with knee osteoarthritis resulted from a systematic qualitative process, including attribute-ranking exercises. A DCE will provide insight into the relative importance of these attributes for participating in physical activity, which can guide intervention development.