  Cold fronts - sharp discontinuities recently discovered by Chandra in many
clusters of galaxies - are believed to be due to a hot gas flow over a colder
gravitationally bound gas cloud. We analyze the stability of the fronts with
respect to Kelvin-Helmholtz instability and show that an intrinsic width of the
interface of the order of a few per cent of the curvature radius strongly
limits the growth of perturbation. For the best studied case of a front in the
Cluster Abell 3667 we conclude that current observational data on the width and
extent of the front can be explained even in the absence of dynamically
important magnetic fields.
