The photoelectrons emerging from unpolarized CO2 and N2O molecules exposed to circularly polarized synchrotron radiation are spin polarized After a brief description of the apparatus the polarizations measured at the ionization threshold are presented and compared in the case of CO2, with a calculated, in an ab initio theory obtained value. Using the spin density matrix formalism a general expression for the spin polarization as a function of the dipole matrix elements is presented.