This publication has been prepared to provide scientific divers with guidance on safe practice under varying experimental and environmental conditions. The Code offers advice and recommendations on administrative practices, insurance, terms of employment, medical standards, training standards, dive planning, safety with different breathing gases and different breathing systems, expedition planning, and guidance for a wide range of different diving environments. Conditions analyzed include: (1) polar diving; (2) cave diving; (3) night diving; (4) diving in the open ocean; (5) diving in surf; and (6) diving at high altitude. Recommendations are also given for the use of various potentially hazardous types of equipment, such as electrical systems, toxic chemicals, and radioactive tracers. The Code does not have the authority of law, and in every country legislation will take precedence over this Code. Nevertheless, it is intended that this document should be compatible with legislation, and should help legislators, diving officers, administrators, heads of laboratories, and divers, to maintain safety at all times. The methods and practices recommended are derived from professional experience at many universities and marine laboratories. There are detailed references to bibliography and addresses of experts. (Author/CW)