The resonant self-induced optical activity (SIOA) in an atomic alkaline metal vapors has been investigated for the first time. Data on optical polarization rotation are presented and interpreted in terms of the resonance behavior of the third order susceptibility and finite elliptical polarization of real lasers. The limiting action of SIOA on the efficiency of resonance parametric generators and polarization spectroscopy is outlined. The observation of a nonlinear resonant self- induced of the laser beam polarization rotation in ruby crystal (Al2O3:Cr3+) at the laser transition are reported.