This is an announcement for the paper "Definability under duality" by Pandelis Dodos. Abstract: It is shown that if $A$ is an analytic class of separable Banach spaces with separable dual, then the set $A^*=\{ Y:\exists X\in A \text{ with } Y\cong X^*\}$ is analytic. The corresponding result for pre-duals is false. Archive classification: math.FA math.LO Mathematics Subject Classification: 03E15, 46B10 Remarks: 9 pages, no figures The source file(s), DualsVersion-ArXiv.tex: 29048 bytes, is(are) stored in gzipped form as 0805.2036.gz with size 9kb. The corresponding postcript file has gzipped size 79kb. Submitted from: pdodos@math.ntua.gr The paper may be downloaded from the archive by web browser from URL http://front.math.ucdavis.edu/0805.2036 or http://arXiv.org/abs/0805.2036 or by email in unzipped form by transmitting an empty message with subject line uget 0805.2036 or in gzipped form by using subject line get 0805.2036 to: math@arXiv.org.