64 patient on chronic haemodialysis were investigated. The duration of the dialysis was 44 months; the mean age of patients was 41 years. In 6 patients a diagnosis of Dementia was made in addition to apraxia, dysarthria and anarthria. 5 of the patients died. All the demented patients showed an abnormal EEG and 4 had atrophy in the computertomogram. The plasma aluminium levels were significantly raised (409 microgram/l) in the demented group as compared to the non-demented dialysis patients (189 microgram/l).