The purpose of this publication is to provide to all concerned in the operation of aeroplanes information on, and guidance in the use of, ground proximity warning systems (GPWS). Legislation regarding the requirement to carry GPWS is to be found in the Air Navigation (Hong Kong) Order 1995. In compliance with ICAO Standards, Airworthiness Directives are issued from time to time which amplify the Order and set out amendments to regulatory requirements as equipment performance advances and as changes in aviation safety-related needs are identified. This document includes information on the different categories of alerts or warnings which may be encountered in flight, together with advice concerning the appropriate flight crew response to each case. The various modes of protection afforded by the equipment are described. However, details of the operating envelopes of the systems are set out in manufacturers’ handbooks or company Operations Manuals which should be studied by all personnel involved in the operation of aeroplanes equipped with GPWS. Information is also presented recommending the details which should be included in Checklists, Operations and Training Manuals.