This is an announcement for the paper "Ito's formula in UMD Banach spaces and regularity of solutions of the Zakai equation" by Z. Brzezniak, J. M. A. M. van Neerven, M. C. Veraar and L. Weis. Abstract: Using the theory of stochastic integration for processes with values in a UMD Banach space developed recently by the authors, an Ito formula is proved which is applied to prove the existence of strong solutions for a class of stochastic evolution equations in UMD Banach spaces. The abstract results are applied to prove regularity in space and time of the solutions of the Zakai equation. Archive classification: math.PR math.FA Mathematics Subject Classification: 60H15; 28C20; 35R60; 46B09; 60B11 Remarks: Accepted for publication in Journal of Differential Equations The source file(s), zakai_01_04-2008_arxiv.tex: 83664 bytes, is(are) stored in gzipped form as 0804.0302.gz with size 25kb. The corresponding postcript file has gzipped size 148kb. Submitted from: mark@profsonline.nl The paper may be downloaded from the archive by web browser from URL http://front.math.ucdavis.edu/0804.0302 or http://arXiv.org/abs/0804.0302 or by email in unzipped form by transmitting an empty message with subject line uget 0804.0302 or in gzipped form by using subject line get 0804.0302 to: math@arXiv.org.