In 1971 during a routine celiac axis injection, 70 cc of room air was inadvertently injected into a patient instead of iodinated contrast. Fortunately, there were no ill effects and despite the use of cut film at the time, Hawkins visualized the celiac axis and its branches as a negative image. Because of this incident, in combination with his previous knowledge of carbon dioxide (CO2) in venous imaging, he began to study the intra-arterial use of CO2 in animals. Following the safe, successful use in animals he applied the same principles to humans. Unfortunately, technology lagged behind his genius and the initial imaging was poor. Later, during the 1980s, there was the development of digital subtraction angiography, tilting tables and a safe, reliable CO2 delivery system. As technology continued to improve, CO2 evolved into a viable vascular imaging agent. Although used initially for renal failure and iodinated contrast allergy, the many unique properties of CO2 yielded multiple advantages, which are now used in a multitude of scenarios alone or in combination with traditional contrast. It has now been used with great success in both adults and children for more than 3 decades with only limited reportable complications. Its safe use in children has been described and when performed in this age group the same principles apply as for adults. This paper describes the history and technique of CO2 angiography for vascular procedures.