OBJECTIVE To assess lipid peroxidation and ultrastructural modifications in rat brains following perinatal exposure to lead (Pb) and/or cadmium (Cd). METHODS Female rats were divided into four groups: control group, Pb (300 mg/L) group, Cd group (10 mg/L) and Pb+Cd (300 mg/L, 10 mg/L) group. The compounds were delivered in the drinking water throughout pregnancy and lactation. RESULTS The levels of compounds in blood and brain of the Pb+Cd group were similar to those of other groups, but the effects of Pb+Cd on pups' body and brain weights were higher than on other compounds. Electron microscopy revealed that Pb and Cd had effects on mitochondrial swelling, disruption and cristae loss, Nissl body dissolution, degenerated organelles and vacuoles, cytomembrane disappearance, and nuclear chromoplasm concentration. The activity of glutathione peroxidase (GSH-Px), superoxide dismutase (SOD), catalase (CAT), acetylcholinesterase (AChE) was decreased, whereas the activity of maleic dialdehyde (MDA) was increased. CONCLUSIONS Perinatal exposure to low doses of Pb and Cd can produce alterations in lipid peroxidation and ultrastructural modifications in rat brains, and exposure to both metals can result in greater damages.