"Health for all by year 2000" was the subject of the WHO Conference at Alma-Ata in 1978. It was evident that good primary care was a requirement to reach this goal. However, knowledge about this was scanty, and the instrument, an acceptable classification for analyses of primary care, was lacking. Since 1978 a WHO Working Party on Classifications of Primary Care has been working on a Reason for Encounter Classification. A RFEC test form was produced. In 1983 a feasibility study was conducted in nine countries: Australia, Barbados, Brazil, Hungary, Malaysia, The Netherlands, Norway, the Philippines, and the USA. The results of this were changing the original proposal very much. In addition, the WONCA/WHO Classification of Health Problems in Primary Care was included in the final version. In 1984 this final version was accepted by WONCA Classification Committee. This is called ICPC = The International Classification of Primary Care. ICPC is biaxial with the chapters of organ/organ systems along the one axis, in addition of three chapters: General, Mental, and Social problems. The other axis comprises seven components: Complaints, Process and Diagnosis. An alphanumeric code is used. The feasibility study of RFEC comprised ten test sites, and 138 primary care professionals recorded a total of 100 452 reasons for encounter. The English version of the RFEC was translated into five other languages, and these versions were used during the study. ICPC is a comprehensive, simple and practicable classification which can be used in medical records and in different areas of primary care research.