Angiotensin II (Ang II) has been shown to accelerate atherogenesis, and the cellular Ang II type 1 (AT(1))-receptor mediates most of Ang II-induced pro-atherogenic effects. In this study we have examined the effect of macrophage oxidative stress on cellular AT(1)-receptor expression. Mouse peritoneal macrophages (MPM) from apolipoprotein-E deficient (E(0)) mice at increasing ages (1 6 months) demonstrated an age-dependent increase in cellular lipid-peroxides (PD) content. In parallel, the AT(1)-receptor mRNA and protein levels both increased by up to 3.7-fold and 1.7-fold, respectively, in MPM from 6-month old mice compared with 1-month old mice. Vitamin E supplementation to E(0) mice significantly decreased the MPM PD content and macrophage AT(1)-receptor mRNA expression compared with placebo-treated mice. The role of oxidative stress in the cellular expression of AT(1)-receptors was further demonstrated by manipulation of macrophage glutathione content. Buthionine-sulfoximine, a glutathione synthesis inhibitor, increased MPM PD content and AT(1)-receptor mRNA expression, whereas L-2-oxothiazolidine-4-carboxylic acid, that contributes to glutathione synthesis, reduced macrophage PD and AT(1)-receptor mRNA expression. Incubation of MPM with oxidised low-density lipoproteins (LDL) led to a significant, dose-dependent and time-dependent increase in macrophage AT(1)-receptor mRNA and protein expression, compared with control cells. In contrast, native LDL or acetylated LDL did not significantly affect macrophage AT(1)-receptor mRNA expression. In conclusion, our findings suggest that oxidative stress in macrophages induces AT(1)-receptor expression. This phenomenon can stimulate the interaction of Ang II with macrophages and hence accelerate macrophage foam cell formation and early atherogenesis.