The Civil Aid Service (CAS) is a government auxiliary emergency service established under the Civil Aid Service Ordinance with an establishment of 3 634 adult volunteers, 3 232 cadets and 115 civil servants.

The primary duty of the CAS is to provide civil support services during emergencies. Adult members of the service are trained to perform emergency duties during typhoons, flooding and landslips; to search for and rescue people in distress in mountains; to help evacuate or rescue victims trapped under collapsed buildings or buried in landslips; and to combat vegetation fires and oil pollution at sea. In 2004, CAS members were mobilised for one typhoon, two flood rescue operations, 41 mountain search and rescue duties, and some 60 vegetation fire-fighting operations.

Every Sunday and public holiday during the dry seasons, the CAS deploys more than 200 members for vegetation fire-fighting and patrolling the numerous hiking trails and country parks. As regards assistance in performing crowd management duties, the CAS participated in 233 public events and deployed 35 members daily at the Lo Wu Control Point. Almost 2,000 CAS members were deployed for crowd management duties during the Legislative Council Election on September 12.

The CAS also provided safety and skill training to government departments, non-governmental organisations and other groups. Training conducted in 2004 included 34 talks on mountain safety and 22 courses on basic mountain search and rescue, safe movements at heights and crowd management. In support of the Pre-employment Training Programme and the Smart Teen Challenge Camp Scheme, the CAS organised under these two programmes respectively, a disciplinary module training course for 34 school leavers and 12 training camps for 1 034 secondary students.

The CAS endeavours to develop leadership potential and cultivate civic awareness among youngsters by recruiting youths aged 12 to 17 into the CAS Cadet Corps. Apart from participating in recreational activities, CAS cadets are trained in a wide variety of disciplines and skills including foot drill, basic emergency rescue, mechanical and electrical knowledge, printing and binding, fibreglass moulding, rock climbing and expeditions. Those cadets over 13 years old are also encouraged to participate in crowd management duties at major community events and to perform hiking trial and country park patrol duties.