The basic behavior of microparticles placed in the Gaussian standing wave is studied theoretically in this article. It is shown that the optical force depends periodically on the particle size and, as the consequence, the equilibrium object position is alternating between the standing wave antinodes and nodes. It is presented that the particle confinement is disabled for certain particle sizes. Simplified theoretical description giving analytical formulae for weak dielectric spherical objects of micrometer sizes is presented. Coincidence with the generalized Lorenz- Mie theory is studied here. Experimental confirmation of the theoretical results is briefly discussed.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.