Scientific symposia on haemoglobinometry were held at the 9th Congress of the European Society of Haematology, Lisbon, 1963 (ESH 1964) and the 10th Congress of the International Society of Haematology (ISH), Stockholm, 1964 (ISH 1965). The International Committee for Standardization in Haematology (ICSH) made recommendations endorsed by the General Assembly of ICSH in Sydney on 23 August 1966 (ICSH 1967), for a reference method for haemoglobinometry and for the manufacture and distribution of an international reference preparation. Further symposia were held at the 12th Congress of the ISH, New York, 1968 (Astaldi, Sirtori & Vanzetti 1979) and at the 13th Congress of ISH, Munich, 1970 (Izak & Lewis 1972). The recommendations were reissued in 1978 (ISH 1978). On the basis of continuing experimental studies, the reference method and the specifications for the international reference preparation have been modified. The revised recommendations are described in this document.