Sickle cell anaemia (SCA) and beta thalassaemia are severe inherited blood disorders. Despite some reports indicating that haemoglobinopathies are the most common serious genetic disorder in the UK, some parts of Europe, Africa and the Caribbean, sickle cell disorders still receive relatively little attention from the public or the healthcare service industry. The aim of this article, the first of two parts, is to provide an overview to the background, causes and incidence of sickle cell disorders in the UK and how an acute crisis state develops. Readers should note that the term 'painful episode' is now used in preference to 'crisis', which suggests catastrophe. The second article will look more closely at the pharmacological treatments for SCA painful episode management.