This report presents the recommendations of a WHO Expert Committee commissioned to coordinate activities leading to the adoption of international requirements for the production and control of vaccines and other biologicals and the establishment of international biological reference materials. The report starts with a discussion of general issues brought to the Committee's attention and provides information on the status and development of reference materials for various antibodies, antibiotics, antigens, blood products and related substances, cytokines and growth factors and other substances for which the Committee has discerned a need for international reference materials. The second part of the report, of particular relevance of manufacturers and national control authorities, contains guidelines for the production and control of synthetic peptide vaccines, requirements for tick-borne encephalitis vaccine (inactivated), guidelines for thromboplastins and plasma used to control oral anticoagulant therapy, an amendment to the requirements for hepatitis B vaccine made by recombinant DNA techniques and a report on the standardization and calibration of cytokine immunoassays.