The silver image tone in water-coated photothermographic materials usually depends on the image density in contrast to that in organic solvent-coated one. It was revealed by TEM observation that the size of developed silver particles depended on the image density owing to the absence of sphere of influence in water-coated photothermographic materials, while it did not in organic solvent-coated ones owing to the presence of sphere of influence. While the morphologies of the developed silver particles were not depend on the image density in this case, the silver image tone was greatly affected by the morphological change resulted from the other developing system such as the toner variation.