Magnetic anisotropy of epitaxial La0.8Ca0.2MnO3(LCMO) thin films grown by pulsed laser deposition has been studied as a function of temperature and lattice strain. Pseudomorphic growth on (001) SrTiO3 substrates imposes an in-plane tensile stress on the LCMO films, which produces an easy-plane magnetic anisotropy in the growth plane, accompanied by a weak biaxial anisotropy in the easy plane. In contrast growth on (001) LaAlO3 substrates produces an in-plane compressive stress, which leads to an out-of-plane uniaxial easy axis. The observed behavior indicates the presence of a positive magnetostriction, and that the anisotropy energy is dominated by the epitaxial strain induced effects. Uniaxial magnetic anisotropy constants of 250 and 500 Å LCMO films have been determined by fitting the magnetization curves for temperatures between 5 and 200 K, and magnetostriction constants have been estimated subsequently. © 2000 American Institute of Physics.