Relaxation processes on the picosecond and subpicosecond time scale after optical excitation have been studied by time-resolved ma,magnetization-induced second-harmonic generation from ferromagnetic nickel. A fast drop of the second-harmonic intensity and the Kerr-signal within 300 fs after optical excitation has been observed which is followed by a partial recovery within a few picoseconds. We show that the fast initial drop cannot be unambiguously attributed to an ultrafast decrease of the magnetization.