Abstract: Macrophages are present throughout the adrenal cortex, particularly in the deeper layers. They locate next to parenchyma cells, which secrete glucocorticoids under the regulation of the pituitary adrenocorticotropic hormone (ACTH). Blockade of ACTH secretion is followed by adrenocortical cell atrophy and apoptosis, an effect likely to cause an increase in local macrophage number and phagocytic activity. The purpose of the current study was to verify this effect and ascertain its age-related variation after ACTH blockade. Male rats at five different ages ranging from 2 to 24 months were divided into two groups, which were injected with dexamethasone phosphate or saline for 3 days. The adrenals were processed for morphological and morphometric study. The age-related increase in macrophage number seen in a survey of the sections was confirmed in the quantitative study: a significant increase in volume density (Vv), numerical density (Nv), and cell volume was found in both groups; Vv and Nv were higher in treated rats. These findings in the deeper layers of the cortex suggest a continuous process of phagocytosis, likely of parenchyma dead cells or their debris, which increases further after ACTH blockade. An additional modulatory effect of macrophages also may occur because of their secretory role.