In December 1989, Portugal presented its candidature to the BIE.
In 1992 the BIE General Assembly voted in favour of the Portuguese bid for the 1998 exhibition.
With Expo98, dedicated to the oceans and held during the year of the 500th anniversary of Vasco da Gama's voyage to India, Portugal invited the whole world to protect the seas, with its motto "the oceans, a legacy for the future".
At the same time, the Intergovernmental Oceanographic Conference, held in Lisbon at the end of 1991, made the link with the proposal for the Lisbon exhibition and approved the project.
In December 1994, as a conclusion to the Portuguese initiative, the General Assembly of the United Nations proclaimed 1998 as the Year of the Oceans. Expo98 introduced two significant variants:
-It seized the opportunity of the event to give an impulse to the development of the city by recovering vast abandoned industrial land on the banks of the Tagus and setting up an exhibition park. This was an integral part of an urbanisation plan covering a total area of 340 hectares of a district to be developed.
-With the national pavilions located in two districts: North and South, and the facilities provided free of charge, nations were encouraged to invest more heavily in their content.