This is an announcement for the paper "Duality of metric entropy" by S. Artstein, V. Milman, and S. J. Szarek. Abstract: For two convex bodies K and T in $R^n$, the covering number of K by T, denoted N(K,T), is defined as the minimal number of translates of T needed to cover K. Let us denote by $K^o$ the polar body of K and by D the euclidean unit ball in $R^n$. We prove that the two functions of t, N(K,tD) and N(D, tK^o), are equivalent in the appropriate sense, uniformly over symmetric convex bodies K in $R^n$ and over positive integers n. In particular, this verifies the duality conjecture for entropy numbers of linear operators, posed by Pietsch in 1972, in the central case when either the domain or the range of the operator is a Hilbert space. Archive classification: Functional Analysis; Metric Geometry Mathematics Subject Classification: 46B10; 47A05; 52C17; 51F99 Remarks: 17 p., LATEX The source file(s), ArtMilSzaAoM.tex: 40692 bytes, is(are) stored in gzipped form as 0407236.gz with size 14kb. The corresponding postcript file has gzipped size 68kb. Submitted from: szarek@cwru.edu The paper may be downloaded from the archive by web browser from URL http://front.math.ucdavis.edu/math.FA/0407236 or http://arXiv.org/abs/math.FA/0407236 or by email in unzipped form by transmitting an empty message with subject line uget 0407236 or in gzipped form by using subject line get 0407236 to: math@arXiv.org.