The aim of OASIS is to provide an efficient and easy-to-use tool for coupling independent general circulation models of the atmosphere and the ocean (AO-GCM) as well as other climate modules (sea-ice, vegetation, wave models...). Coupled GCMs (CGCMs) are the necessary tools to tackle current climatic paradigms such as the El Niņo Southern Oscillation (ENSO) or the greenhouse gases global warming effect. The models can possibly run on various plateforms and in different environments (batch mode, interactive mode...). Modularity and flexibility have been particularly emphasized in the OASIS design. The use of OASIS does not change the way the models were previously running, except that it requires the addition of few communication routines. In case one wants to run distributed simulations, PVM version 3.3 or later needs to be installed on the different platforms.