Respiratory diseases in dogs and cats can be classified into respiratory problems brought about as a result of a specific abnormality of the respiratory system; so called primary respiratory disease, and bronchopulmonary problems which occur as a consequence of heart failure; so called secondary respiratory disease. This section will concentrate predominantly on considerations regarding the treatment of primary respiratory diseases. This includes agents used to facilitate bronchodilation, to reduce coughing and various expectorants and mucolytics. In addition, the optimal fluid therapy and various ways of oxygen delivery with complication will be discussed with emphasis In order to understand the indications for, and action of, various drugs used in the treatment of respiratory disease an understanding of normal respiratory physiology is important and these considerations is described in this section for helping to understand further for readers.