A recent body of work introduced new tight-frames of curvelets E. Cantles, D. Donoho, in: (i) Curvelets - a suprisingly effective nonadaptive representation for objects with edges (A. Cohen, C. Rabut, L. Schumaker (Eds.)), Vanderbilt University Press, Nashville, 2000, pp. 105-120; (ii) http://www.acm.caltech.edu/similar toemmanuel/publications.html, 2002 to address key problems in approximation theory and image processing. This paper shows that curvelets essentially provide optimally sparse representations of Fourier Integral Operators. (C) 2003 Academic des sciences/Editions scientifiques et medicales Elsevier SAS. All rights reserved.