SCIENTIFIC ABSTRACT We propose to observe with the ISO-SWS a carefully selected sample of bright AGB stars, varying from Mira variables with little mass loss to very cool OH/IR stars and extreme carbon stars experiencing heavy mass loss. A few S-stars and M-type supergiants are included as well. On the basis of ISO-SWS data of these stars we expect to significantly improve our understanding of the evolution, the variation of the mass loss rate with time and the chemical composition of the circumstellar shells of AGB stars. Sources will be observed over the whole wavelenght range with the AOT SWS01, Low-Resolution Full Grating Scan. The total dedicated target time requested for this proposal amounts to 16h38m08s (40 sources) in case of a Spring launch, and 16h38m26s (41 sources) hours in case of an Autumn launch. OBSERVATION SUMMARY For all the sources spectra will be obtained covering the full SWS wavelength range from 2.4 to 45 mic. Three of the brightest sources will be observed with the AOT SWS01-3 in order to reach half of the full resolution (integration time = 50 mn), the others will be observed with the AOT SWS01-1 (low resolution, integration time = 13 mn), and three fainter sources with the AOT SWS01-2 (integration time = 25 mn, see Tables 3 and 4). We expect a signal-to-noise ratio (much) larger than 10 for all the sources, except at the shortest wavelengths for a few very optically sources. The total number of sources to be observed amounts to 40 for a Spring launch and 41 for an Autumn launch. The total dedicated target time requested amounts to 16h38m08s and 16h38m26s for a Spring and an Autumn launch respectively.