Aim: Detailed information regarding the causes and treatment of acute collapse in the cat can be difficult to locate in a single published source. This two-part review aims to provide a logical approach to the clinical assessment and stabilisation of the critically ill collapsed cat. Practical relevance: Cats are particularly challenging when presented as emergency patients, often in the later stages of an illness or with a vague history and non-specific signs. The nuances of the critically ill cat are considered, especially for shock and its management. Clinical challenges: Shocked cats do not present in the classic stages typically seen in dogs, and the signs are more subtle. Therefore, the clinician must consider whether physical parameters are appropriate for the state and environment of the patient; for example, a normal heart rate in a shocked cat would be considered inappropriate. Audience: This review is directed at any veterinarian working with feline patients, and particularly those dealing with emergencies on a regular basis. Evidence base: There is an extensive body of published literature, both original studies and textbook chapters, pertaining to the causes and treatment of collapse in the cat. In this article the authors draw on information from original publications, reviews and their clinical experience to provide practical guidance to assist in the emergency setting.