Let A be a selfadjoint operator. We are interested in the discrete spectrum of B = A+M where B is non-selfadjoint. If the resolvent difference 
 is in the Schatten class S_p, then we have an estimate on the distribution of the eigenvalues of B. By means of this estimate we can give 
 qualitative estimates for the number of eigenvalues of B or their moments. That can be applied to Schodinger operators with complex potentials.