The effect of intramuscular administration of alpha 1-adreno-stimulator phenylephrine (standard dose of 0.15 mg/kg body wt.) on the chronotropic, pump, systolic, and diastolic heart function, renal blood circulation and microcirculation in different vessel regions was studied in 60 healthy human subjects of different ages (20-34, 60-74, and 75-89 years). In aging, the overall effect of standard phenylephrine dosage has been found to decrease. Parallel to this, there was a change in the structure of the response of cardiovascular system to alpha 1-adreno-stimulaor administration. In older population groups, the positive effect of phenylephrine upon the pump and systolic heart function decreased, while its negative effect on the renal blood circulation and microcirculation in different vascular regions increased.