Aluminium (Al) is neurotoxic and a relationship between Alzheimer's disease (AD) and Al in drinking water has been suggested in epidemiological studies. In 5 patients with AD, and healthy subjects of whom 5 were aged, 6 were middle-aged and 6 were young adults, Al excretion into the urine was measured using inductively coupled plasma emission spectro-analysis. In healthy subjects, there appeared to be a relationship between age and daily Al excretion, with the highest level in the aged group, followed by the middle-aged and young adult groups. A significant positive correlation between the amount of urine and the Al excretion in the healthy subjects was also observed. Daily A1 excretion in urine in the group of patients with AD tended to be higher than that of the age matched healthy group, but further studies are needed to account for effects of drugs containing Al compounds. The Al excretion in all the groups showed some variation with the time of day, but no definite diurnal variation common to all the subjects was noted. Because of this, the use of spot urine analysis for studying A1 excretion does not seem to be reliable.