A mixture of linoleic and α-linolenic acids (free non-esterified unsaturated fatty acids) administered for 3 weeks prior to injection of cortisol (10 mg/kg), or prior to immersion of rats in a 10d`C saline bath, prevented elevation of blood levels of cortisol and cholesterol and deficits in Morris water maze spatial learning that usually accompany such stressful conditions. Differences from controls on all behavioural and biochemical measures were statistically significant (P <. 05). It is proposed that induction of intense stress, and the associated increase in cortisol, cholesterol and other corticosteroids may damage hip-pocampal structures and help account for the cognitive decline witnessed in Alzheimer's disease and other age-related conditions. The modulation of these consequences by the fatty acid mixture may provide an alternative strategy for the study of stress markers and for the development of other intervention options in humans.