The purpose of the paper is to reveal the dependence of platelet activity level in rats on the age of their experi- mental dyslipidemia. The study included 105 healthy male rats (34 rats aged 12 months, 32 rats aged 18 months, and 39 rats aged 24 months) with modeled dyslipidemia. The control group included 91 healthy male rats (30 animals aged 12 months, 32 rats aged 18 months, and 29 animals aged 24 months) under standard vivarium conditions. Biochemical, hematological, and statistical methods were applied. Gradual increasing of functional platelet activity was noticed in the control rats with increasing age. Alimentary modeling of dyslipidemia in the rats resulted in marked platelet-activity increase, growing with the increase in the experimental animals' age. Dyslipidemia modeling in the rats of different age showed the weakening of plasma antioxidant protection and increase in plasma LPO, deepening with the increase in the studied animals' age. The developing disorders in the experimental rats exceeded the age-related changes of platelet activity in the control. © 2016 Zavalishina et al.