A microscopic many‐body model is proposed for the kinetics of metastable defects (MSDs) in hydrogenated amorphous silicon (a‐Si:H). It is based on the existence of short‐lived large energy fluctuations which induce transient traps for carriers that release their energy and enhance the creation or annihilation of MSDs. The expressions found for the photoinduced and thermally induced creation and annihilation rates’ coefficients explain the dependence on the variety of parameters. ©1995 American Institute of Physics.