Medial temporal lobe structures may be important for memory. We examined the cognitive, brain atrophy, and sociomedical correlates of medial temporal lobe atrophy (MTA) in 59 individuals (79.2 +/- 4.6 years old) randomly selected from a population-based study within strata of age and severity of clinically assessed DSM-III-R dementia (45 clinically normal and 14 mild/severely demented). MTA was qualitatively assessed on coronal T-1-weighted MRI. Thirty-three percent of the sample showed MTA, which was associated with dementia severity (p < 0.01), and cortical and white matter atrophy. MTA was not associated with age, education, sex, depressive symptoms, or presence of infarction. Controlling for age, education, and associated brain atrophy, those with MTA performed more poorly on a general test of cognitive function (the neuropsychological test component of the Cambridge Examination for Mental Disorders of the Elderly; p < 0.04) and its subtests of memory function (p < 0.02) and memory-related functions, including perception, fluency, and orientation (p < 0.05). In the clinically normal subsample, those with MTA performed more poorly on the memory function (p < 0.05) subtests. We conclude that MTA is common among very old persons, is associated with other brain abnormalities implicated in cognitive function, but may specifically contribute to memory dysfunction in the general population of very old persons.