In situ investigation of metallic silver formation, resulting from the thermal decomposition of silver myristate and from the thermally induced reduction of silver myristate incorporated into a photothermographic imaging construction, shows that the metallic silver formed is different in the two systems. The thermal decomposition of this silver carboxylate produces larger metallic silver crystallites than the thermally induced reduction process, which can be attributed to the silver growing within the constraints of the solid state crystal lattice in the former, compared to the transport of silver ions to the development sites in the latter. The conversion of silver ions to metallic silver in the decomposition process occurs only after the silver carboxylate crystallites pass through several solid state phases.