Chronic total occlusions (CTO) are complete obstructions of coronary arteries, of more than 3 months duration and with poor or no antegrade blood flow. Cardiac imaging is important which helps in selecting patients most likely to benefit from revascularization as well as for preprocedural planning, postprocedural assessment of revascularized segments and long-term outcomes studies. The most common failure mode of CTO interventions remains the inability to successfully cross the occlusion with a guidewire. In this chapter incidence and presentation of CTO, algorithm for crossing CTO, guidewire selection and utilization, complications associated with CTO, success rate of CTO, challenges of CTO lesions are all discussed in detail.