A new poly(L-lactide) (PLA)-degrading actinomycete, Kibdelosporangium aridum, degraded more than 97 mg out of 100 mg added high molecular weight PLA film (Mn: 3.4 x 10(5)) within 14 d in liquid culture. L-Lactic acid, the monomeric degradation product of PLA, was totally assimilated by the strain. In solid culture, many distinct grooves formed by the morphology of filamentous microorganisms on the surface of a PLA film were observed by scanning electron microscopy.