Awareness of memory loss was rated in 57 patients with clinically diagnosed Alzheimer's disease, and analyzed in relation to neuropsychological tests and presence of depression. Single photon emission computed tomography measures of regional cerebral blood flow were obtained on an unselected subsample of 20. Anosognosia was associated with diminished relative right dorsolateral frontal lobe perfusion and with high rates of false positive errors on recognition memory testing. Less aware patients did not differ from others on learning or recall scores, or on dementia severity as measured by mental status scores. Neither anosognosia nor depression was associated with disease duration or dementia severity and patients who were aware of their memory loss were no more likely than others to be depressed. This is further evidence that dementia severity alone does not account for anosognosia in Alzheimer's disease; frontal lobe involvement and the presence of specific memory impairments may be important determining factors.