There is little information dealing specifically with motor neuron disease (MND) in the elderly. Given current epidemiological trends, geriatricians will be increasingly called upon to diagnose and manage this condition. We report four patients who presented within a six month period to a geriatric medical unit, and place this experience in the perspective of 229 patients from a population-based study of adult-onset MND in Scotland in 1989 and 1990. In 1990 Scotland had a crude annual incidence of MND of 2.25/100,000; the figure for those over 65 is four times greater. MND is more common in men, but the sex ratio was nearly equal over the age of 65. The risk of presenting with bulbar palsy was greater in women, and even higher in elderly women. This, together with increasing age, is the most important negative prognostic factor in MND. Problems with the diagnosis and management of MND in the elderly are highlighted.