Primary ciliary dyskinesia (PCD) is usually inherited as an autosomal recessive, and in classical form presents with upper and lower respiratory tract infection, and mirror image arrangement in around 50% cases. It is becoming appreciated that dysfunction of cilia is implicated in a wider spectrum of disease, including polycystic liver and kidney disease, central nervous system problems including retinopathy and hydrocephalus, and biliary atresia. Cilia are complex structures, containing more than 250 proteins, but recent studies have begun to locate PCD genes scattered throughout the genome. Screening tests for PCD include nasal nitric oxide and in vivo tests of ciliary motility such as the saccharin test. Specific diagnosis requires examination of cilia by light and electron microscopy, with epithelial culture in doubtful cases. This is only available in supra-regional centres, which have recently been centrally funded by NCG in order to provide a comprehensive, free diagnostic service in England. Treatment is unfortunately not evidence based, since there are no randomised controlled clinical trials in this condition, and recommendations are largely extrapolated from cystic fibrosis and other suppurative lung diseases.