The variability of line profiles in spectra of bright OB stars has been studied. We obtain more than 1000 high quality spectra of δ Ori A, λ Ori A, α Cam, 19 Cep, l Her, ρ Leo and other target stars. We revealed the line profile microvariability of small amplitude (0.5-3% in the adjacent continuum units) for all observed stars. For most stars only cyclic components of the line profile variability (LPV) at the time scales from hours to days were detected. These components seem to be connected with both the non-radial pulsations (NRP) and rotation line profile modulation. In the spectra of δ Ori A and λ Ori A we found the evidences of the stochastic LPV in spectra, probably connected with the small clumps in the stellar wind. On the basis of recent observations we discuss the origin of the magnetic field of early-type stars.