Peripheral arterial disease (PAD) is caused by occlusive atherosclerosis in a vascular bed other than the heart. The lower extremity is the most-common location for PAD. Critical limb ischaemia (CLI) is the most-severe clinical manifestation of PAD. Despite improvements in medical care and revascularization, patients with CLI continue to have a high risk of major amputation (below the knee or higher) and cardiovascular death. The primary goal of therapy in CLI is to achieve blood flow to the distal limb vessels with angioplasty or bypass surgery. However, many patients with CLI are unsuitable for revascularization, or the procedure is unsuccessful. Angiogenesis is the growth and proliferation of blood vessels from an existing vascular structure. In therapeutic angiogenesis, attempts are made to utilize blood vessel growth to augment perfusion. In this Review, data from phase II and III clinical trials of therapeutic angiogenesis in patients with PAD will be presented and discussed. Potential explanations for the limited success of therapeutic angiogenesis in humans will be viewed in the context of advances in our understanding of the complex mechanisms underlying angiogenesis and vascular remodelling. This Review will also cover how advances in systems biology, genetics, and gene therapy might still allow the development of new approaches to therapeutic angiogenesis and achieve the goal of restoring perfusion.