Alopecia areata (AA) is a common cause of reversible hair loss afflicting approximately 1-2% of the general population. It commonly presents itself as round patches of hair loss. The aetiology of AA is unknown but is characterised by hair cycle dysfunction and the presence of peribulbar and perifollicular mononuclear cell infiltrates. In this book, the authors present current research in the study of the causes, diagnosis and treatment of alopecia. Topics include radiation treatment and alopecia; the psychosocial aspects in alopecia areata; the classification, pathogenesis and treatment in alopecia areata and its genetic basis.