Given the importance of understanding CLI patients' outcomes and existing gaps in knowledge, there is a pressing need to collect observational data on treatment patterns, adherence to performance measures, and outcomes that are relevant to patients and clinicians. To address this need, the current study will pilot test the research infrastructure and data elements needed to build a larger, national study collecting of the CLI population. It will also provide much-needed preliminary information to identify areas of action that can be targeted in quality improvement programs for this population. Most importantly, it will provide data on health status outcomes in patients with CLI, as a function of individual patient characteristics (demographics, socio-economic and clinical background) and the treatments that patients have undergone. The PORTRAIT-CLI study will also be well equipped to identify potential disparities in the provision of care and patients' outcomes as a function of patient's characteristics.