A review of recent experiments in the field of femtosecond spin dynamics in ferromagnetic metals is presented. The specific use of thin films is emphasized. One of the crucial problems in the interpretation of the time-resolved magneto-optical experiments is the separation of true magnetization dynamics and optical artifacts, such as state-filling effects. We demonstrate that a full separation can be achieved measuring the laser-induced magneto-optical rotation and ellipticity explicitly. We discuss a procedure to extract the true demagnetization time for the specific case of an epitaxial nickel wedge grown on a Cu(111) substrate. Phenomenological models for the heat diffusion and magnetization dynamics are presented.