The antioxidant properties of appropriate 1-(phenoxyethyl)-piperazine derivatives possessing significant hypotensive activity in normotensive rats were measured in human venous blood samples, in vitro. Ferric reducing ability of plasma (FRAP) was measured in plasma, superoxide dismutase (SOD) and catalase (CAT) activities were determined in red blood cell hemolysates. Antioxidant profile of 1-(phenoxyethyl)-piperazine derivatives was compared to Trolox and Resveratrol. The compounds were investigated in concentrations from 10(-8) to 10(-4) mol x L(-1). The most promising compounds were 1-[(4-methyl)- and 1-[(2,6-dimethyl)-phenoxyethyl]-piperazine derivatives [1, 2] which increased SOD activity and total antioxidant capacity (TAC). An addition of chlorine atom to methyl-phenoxy moiety decreased antioxidant properties.