This is an announcement for the paper "More mixed Tsirelson spaces that are not isomorphic to their modified versions" by Denny H. Leung and Wee-Kee Tang. Abstract: The class of mixed Tsirelson spaces is an important source of examples in the recent development of the structure theory of Banach spaces. The related class of modifed mixed Tsirelson spaces has also been well studied. In the present paper, we investigate the problem of comparing isomorphically the mixed Tsirelson space T[(S_n,\theta_{n})_{n=1}^{\infty}] and its modified version T_{M}[(S_{n},\theta_{n})_{n=1}^{\infty}]. It is shown that these spaces are not isomorphic for a large class of parameters (\theta_{n}). Archive classification: Functional Analysis Mathematics Subject Classification: 46B20; 46B45 The source file(s), LeungTangModMTS.tex: 95277 bytes, is(are) stored in gzipped form as 0601542.gz with size 23kb. The corresponding postcript file has gzipped size 117kb. Submitted from: wktang@nie.edu.sg The paper may be downloaded from the archive by web browser from URL http://front.math.ucdavis.edu/math.FA/0601542 or http://arXiv.org/abs/math.FA/0601542 or by email in unzipped form by transmitting an empty message with subject line uget 0601542 or in gzipped form by using subject line get 0601542 to: math@arXiv.org.