The medical records of 50 patients with a diagnosis of presenile dementia supported by radiological evidence of cerebral atrophy were examined for antecedent manifestations of depressive illness. Symptoms consistent with major affective disorder were present in one half and depressive spectrum diagnoses were made in one fourth of the cases prior to final diagnosis. A history of psychiatric treatment was common and was significantly more frequent in females than males, suggesting the possibility of sex-related bias. The findings demonstrate that presenile dementia is often occult, masked by superimposed symptoms and signs of depressive disorder.