The methanolic product of assai(Euterpe oleracea Mart) scavenged the intracellular reactive oxygen species (ROS) and 1,1-diphenyl-2- picrylhydrazyl (DPPH) radical, and prevented lipid peroxidation. The radical-scavenging activity of assai palm methanolic extract protected the viability of peritoneal macrophage cells exposed to hydrogen peroxide($H_2O_2$). Furthermore, the extract reduced the apoptotic-cell formation induced by $H_2O_2$, as demonstrated by the decrease in the number of hypodiploid cells and in the apoptotic-cell body formation. These results indicate that assai palm methanolic extract has radical-scavenging activity and ameliorates $H_2O_2$-induced cytotoxicity.