Brain monoamine concentrations were determined post mortem in 19 patients with dementia of Alzheimer type. Samples were taken from 10 parts of the brain and compared with an age-matched control group. There were lower mean concentrations of dopamine in the demented group of patients in seven regions of the brain, and two of these were at a significant level. There were also significantly lower concentrations of homovanillic acid in the nucleus caudatus and in the putamen. The means of the concentrations of noradrenaline were also lower, and in the putamen and the cortex gyrus frontalis significant differnces were observed. The 5-hydroxytryptamine concentrations were slightly lower in the demented group but the differences did not reach significance. The degree of intellectual deterioration was negatively correlated with the noradrenaline concentrations in the hypothalamus and the cortex gyrus cinguli.