General analysis of energy transport and momentum density of a paraxial light beam is presented. Usually these exist transverse components of which the tangential one corresponds to energy circulation around the beam axis. This circulation produces the mechanical angular momentum of the beam that exists independently on polarization state of radiation. In particular, non-zero angular momentum is typical for the beam with wave front dislocation; e.g., angular momentum of a Laguerre-Gaussian beam with axial symmetry and zero magnitude at the axis beam has the same value that a plane circularly polarized wave of equal energy holds.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.