Accumulation of [111In]antimyosin in various types of tumors has been reported. In order to test the possibility that the destruction of muscle tissue by tumor invasion could induce high uptake of [111In]antimyosin, we investigated the distribution of [111In]antimyosin in tumor and muscle using autoradiography (ARG). High uptake of [111In]antimyosin was observed both in rabbit papilloma VX2 and rat hepatoma AH109A by scintigraphy and tissue distribution studies, and its concentration was found to be highest at the periphery and outer surface of the tumors using whole-body ARG. However, in micro- and macro-ARG, high grain density was observed in granulation tissue with macrophage infiltration between the tumor and muscle, not in the muscle tissue invaded by tumor cell. Significant non-specific accumulation of [111In]antimyosin in inflammatory tissue surrounding the tumor was suggested.