From the earliest date, the BIE has accepted the need to differentiate between two categories of exhibitions: major events which last for six months and with a theme of a general nature and shorter, more economical events, where the theme is more precise and specialised.

The two categories of exhibitions and their distinctive characteristics are as follows (more information www.bie-paris.org) :

International Registered Exhibition (or World Exhibition)

Frequency : every five years

Duration : 6 months at most

Area : not restricted

Theme : general (cf. General classification for International exhibitions)

International Recognised Exhibition

Frequency : during the interval between two International Registered Exhibitions

Duration : 3 months at most

Area : 25 ha at most

Theme : specialized

This type of event could give all nations the possibility of hosting an international exhibition.

The BIE will also continue to recognise those Horticultural Exhibitions such as the Netherlands Floriade 2002 and IGA 2003 Rostock in Germany, recommended to it by the International Association of Horticultural Producers (AIPH), and the Milan Triennale, an exhibition of long standing featuring the decorative arts.

Since 1928 the BIE's work has been dedicated to identifying and refining the role of those exhibitions within its concern as a means of promoting international goodwill and of exploring the limits of human experience and knowledge.