Plasma levels of triglycerides, cholesterol, cholesterol esters, phospholipids, lipoperoxides, vitamin E and erythrocyte glutathione peroxidase activity showed no significant differences between 40 women with habitual abortion and controls. However, the levels of free fatty acids (FFA), which are extremely cytotoxic compounds, were significantly higher in women with habitual abortion (HA) than in controls (16.8 ± 6.7 vs. 8.6 ± 3.7mg/l00ml, p < 0.01, respectively). The high amounts of FFA in HA women during pregnancy were probably due to a continuous and/or excessive stress-dependent discharge into the blood of catecholamines from autonomic nerve endings. These catechol-amines can induce a strong uterine vasoconstriction and placental ischemia-hypoxia which, in association with additional insults caused by reoxygenation, might lead to eventual miscarriage.