The results of a search for line profile variability (LPV) and polarimetric line profile variability (pLPV) in spectra of O stars are reported. The observations were made with the 1.8-m telescope of the Korean Bohyunsan Optical Astronomical Observatory (BOAO) and the 1-m and 6-m telescopes of the Special Astrophysical Observatory (SAO), Russia. Regular LPV in the spectra of all program stars are found. We analyze the connection between the presence of magnetic field and nitrogen abundance anomalies, and the influence of weak magnetic fields on pLPV. The statistical properties of mean magnetic fields and magnetic fluxes of OB stars are studied.