Abstract In the present paper a phenomenological theory of external factor effects upon amorphous solid properties is presented and applied to some examples. Electric current and laser light effects are considered, but the theory can be generalized to include other effects, e.g., ionizing radiation, chemical reactants etc. Changes of amorphous solid properties are considered as initiated locally and propagated along certain lines, narrow stripes or tubes, which will be called current- or laser traces. The proposed theory consists of the kinetics of the traces’ appearance, development and disappearance, and of the kinetics of processes (physical, chemical a. o.) which occur inside traces. This phenomenological theory is applied to determine the molecular mechanisms of the considered processes by comparing the kinetics obtained theoretically and experimentally for relevant cases. The comparison also allows determination of constants and functions that cannot be calculated theoretically. A possibility was considered that properties change by crystallization, e.g., initiated by resonance electron collisions with atoms, molecules and ions within the amorphous solid. It is shown how the obtained kinetic dependencies can be compared with experimental data to check the hypothesis itself on the resonance mechanism and to determine what are namely resonances contributing to these processes.