With the global epidemic of diabetes, diagnosis of critical limb ischemia (CLI) has become very complex due to mixture of microangiopathy, infection and sometimes neuropathy with the pure ischemia. We still sometimes encounter the patients with extensive tissue loss due to misdiagnosis of ischemia or infection in previous hospital. For adequate decision making of proper treatment selection for each critical ischemic limb without missing the adequate intervention timing, a new classification system good for not only vascular specialists but also gate keeping clinicians working in the era of diabetes has been desired. Responding to marked demographic shift, Society for Vascular Surgery issued new classification named WIfI system which evaluate the foot lesion comprehensively by three factors; Wound (W), Ischemia (I), and foot Infection (fI). Guidelines for peripheral arterial disease recommend use of WIfI classification system. To decide treatment strategy of CLI as well as managing those limbs after revascularization, it is important to popularize adequate diagnostic system using WIfI classification as common language by not only for vascular specialists but also other clinicians facing CLI patients. (This is a translation of Jpn J Vasc Surg 2018; 27: 187-195.).