SUMMARY: Changes in the microcirculation of multiple tissues and organs have been implicated as a possible mechanism in physiological aging. In particular, vascular endothelial growth factor is a secretory protein responsible for regulating angiogenesis via altering endothelial proliferation, survival, migration, extracellular matrix degradation and cell permeability. The aim of the present study was to evaluate the role of vascular endothelial growth factor in the progression of morphological alterations caused by physiological aging in the heart and kidney and to examine its relation to changes in capillary density. We used two age groups of healthy Wistar rats - 6- and 12-month- old. The expression of vascular endothelial growth factor was examined through immunohistochemistry and immunofluorescence and assessed semi-quantitatively. Changes in capillary density were evaluated statistically and correlated with the expression of vascular endothelial growth factor. We reported stronger immunoreactivity for vascular endothelial growth factor in the left compared to the right ventricle and also observed an increase in its expression in both ventricles in older animals. Contrasting results were reported for the renal cortex and medulla. Capillary density decreased statistically in all examined structures as aging progressed. The studied correlations were statistically significant in the two ventricles in 12-month-old animals and in the renal cortex of both age groups. Our results shed light on some changes in the microcirculation that take place as aging advances and likely contribute to impairment in the function of the examined organs.