Several months before the first IPhO took place, invitations were sent to all the Central European countries. The invitations were accepted by Bulgaria, Czechoslovakia, Hungary and Romania (five countries including Poland, the organizer of the competition). Each team consisted of three secondary school students accompanied by one supervisor. The competition was arranged along the lines of the final stage of the Polish Physics Olympiad: one day for theoretical problems and one day for carrying out an experiment. One obvious difference was that the participants had to wait for the scripts to be marked. During the waiting period the organizers arranged two excursions by plane to Krak and to Gdansk. At the first IPhO the students had to solve four theoretical problems and one experimental problem.
The second Olympiad was organized by Prof. Rezs? Kunfalvi in Budapest, Hungary, in 1968. Eight countries took part in that competition. The German Democratic Republic, the Soviet Union and Yugoslavia joined the participating countries. Again, each country was represented by three secondary school students and one supervisor. Some time before the second IPhO a preliminary version of the Statutes and the Syllabus were produced. Later these documents were officially accepted by the International Board consisting of the supervisors of the teams that participated in the competition. This took place during a special meeting organized in Brno, Czechoslovakia, several months after the second IPhO.
The third IPhO was arranged by Prof. Rostislav Kostial in Brno, Czechoslovakia, in 1969. On that occasion each team consisted of five students and two supervisors. The competition in Brno was organized according to the official Statutes accepted earlier.
The next Olympiad took place in Moscow, Soviet Union, in 1970. Each country was represented by six students and two supervisors. During that Olympiad several small changes were introduced into the Statutes.
Since the fifth IPhO, held in Sofia, Bulgaria, in 1971, each team has consisted of five pupils and two supervisors. In 1978 and 1980, the IPhO was not organized. This was due to the accession of the Western countries. The first capitalist country to participate was the Federal Republic of Germany. At first, the few Western countries participating declined to accept the principle that the IPhO be organized every second year in a Western and Eastern block country. Thus the Eastern block countries declined from organizing the 1978 and 1980 olympiads. From 1982 onwards, the yearly competition was resumed as there were enough participating Western countries to share the load. At present, the venue of the olympiad is decided for years ahead. After accession into IPhO, every country must notify the others within three years about its willingness to host the IPhO. After this, the country is placed on a waiting list which as of 2006 stretches well into 2050's. The failure to organize the IPhO on turn will lead to temporary expulsion from the IPhO. This happened e.g. to France in 2000.