We present an experimental and numerical investigation on the statistical properties of the surface elevation in crossing sea conditions. Experiments are performed in a very large wave basin (70 m x 50 m x 3 m) and numerical results are obtained using a higher order method for solving the Euler equations. Both experimental and numerical results indicate that the number of extreme events depends on the angle between the two interacting systems. This outcome is supported by recent theoretical investigations which have highlighted that the instability of wave packets may be triggered by the nonlinear interactions between coexisting, non-collinear wave systems. Citation: Toffoli, A., E. M. Bitner-Gregersen, A. R. Osborne, M. Serio, J. Monbaliu, and M. Onorato (2011), Extreme waves in random crossing seas: Laboratory experiments and numerical simulations, Geophys. Res. Lett., 38, L06605, doi: 10.1029/2011GL046827.