This self-study is designed to provide an introduction into the clinical use of Capnography in veterinary medicine. The measurement of end-tidal CO2 (EtCO2) is currently the optimal method of non-invasively and continuously monitoring the adequacy of ventilation and circulation in veterinary patients. The EtCO2 monitor non-invasively measures expired carbon dioxide and can be of value in the assessment of ventilation, metabolism and circulatory status. This self-study will define the role of EtCO2 and review various applications of this monitor as well as illustrate the relationship between arterial carbon dioxide levels and end-tidal carbon dioxide levels. Commonly encountered capnographic waveforms will also be discussed.