The generalized and fully analytical theory of quantum fluctuations was applied in the study of vertical-cavity surface-emitting lasers (VCSEL's). The quantum Stokes parameters were derived to describe the quantum self-correlations and cross correlations between two polarization components of the electromagnetic fields generated by these lasers. The typical fluctuations and cross-correlation spectra were calculated analytically and represented graphically. It was demonstrated that in certain situations VCSEL's can exhibit polarization squeezing over some range of spectral frequencies.