Premature ovarian failure (POF) is common, affecting approximately 1% of women. It is defined as gonadal failure before the age of 40 and patients may clinically present with either primary or secondary amenorrhoea. This review concentrates on the clinical aspects of POF, with sequential discussion on the aetiology and epidemiology, clinical manifestations and relevant investigations, concluding with an overview of management. In addition, the scientific basis for our current understanding of POF is summarized to provide a comprehensive overview of the diverse pathophysiological mechanisms that may underlie this disorder. Despite the heterogeneity of causes of POF, the fundamental treatment principles are the same. In this review the initiation of hormone replacement therapy in the younger woman and the importance of long term follow-up and treatment are emphasized.