The efficiency of dielectric particle confinement with 790-nm AlGaAs laser diode optical traps is investigated as a function of beam magnification and polarization state. When an anamorphic prism pair is used to correct for diode beam ellipticity, trapping efficiencies of nearly 0.37 are achieved with a magnification factor of 3X, laser powers of 4-18 mW, and an overfilled microscope objective entrance aperture. Results are compared for diodes having small (8 μm) and large (57 μm) astigmatisms, but comparable far-field divergence angles. © 1994 IEEE