Athletes and teams are required to compete in a variety of environmental conditions, and perform to their usual standards. The extremes of these conditions can affect participating athletes in a variety of ways, including aggravating pre-existing medical conditions, causing illness or injury and at times result in medical emergencies. Acclimatisation to the extremes is vital for optimal athlete performance. The aim of the following modules is to improve the users understanding of how environmental extremes affect performance, how to prevent illness and injury in these situations and how to recognise an unwell athlete training and/or competing under environmental extremes. These modules will discuss how best to manage an athlete affected by heat, cold or altitude. The physiology and practical considerations of, contraindications to, and possible consequences of scuba diving are discussed.