Measures of gait and balance were undertaken in 11 elderly ambulant patients suffering from senile dementia of Alzheimer type of moderate severity, and in an equal number of healthy non-demented age- and sex-matched controls. Valid results were obtained in nine pairs. Compared with the controls the demented patients had significantly shorter step length, lower gait speed, lower stepping frequency, greater step-to-step variability, greater double support ratio and greater sway path. The findings are consistent with the view that transcortical pathways participating in the integration of gait are damaged in senile dementia of Alzheimer type. The findings may help to explain the increased incidence of falls in patients with brain failure.