Considering nucleation of dislocation half‐loops from the crystal growth surface as a mechanism of generation of misfit dislocations between an epitaxial film and a substrate, critical thicknesses can be determined by calculating the zero of free energy of the system according to van de Leuretal.’s model [J. Appl. Phys.64, 3043(1988)]. On estimating the free energy, two analytical methods are adopted; one is the whole‐space approximation and another treats surface half‐loops in the half‐space by the image stress construction. In both of the methods, interaction between the two dislocation glide loops either lying in the identical slip plane or lying in the parallel slip planes are incorporated into the analysis. It is shown that half‐loop correction reduces critical thickness, the former interaction reduces and the latter interaction increases it, and the interaction effects become smaller by the half‐space correction. Finally, it is also shown that the effect of anisotropy in the whole‐space approximation tends to increase critical thickness. ©1995 American Institute of Physics.