When compared with control, fibroblasts in granulom which was previously in vivo treated with chloroquine diphosphate showed the following changes. 1) The nucleoplasm partially formed abnormal, scattered, small conglomerates. 2) The granules and intracytoplasmic membraneous bodies resembling myelin figure increased in number. 3) Vacuoles containing homogeneous substance increased in number. 4) Large empty vacuoles increased in number. In summary, it may be concluded that the effect exerted by chloroquine diphosphate on the morphology of fibroblasts in granulom is a change of their ultrastructures suggesting a mild cellular degeneration.