To determine whether bradykinesia in patients with Alzheimer's disease is different from the slowing of movement seen in normal aging, 25 patients with mild to moderately severe Alzheimer's disease and 25 normal controls, matched for age and sex, were studied. The measures of motor performance included two computerized tests of finger tapping, one test of point-to-point arm movements, and one test of gait cadence. Patients performed significantly more slowly than controls on all three types of motor speed measurements, with average decrements of 9% to 19%. Right index finger tapping, right arm point-to-point, and left arm point-to-point tests produced the most significant discrimination of patients from controls. One month test-retest reliability in patients was high for these measures. Bradykinesia measured by these tests was correlated with cognitive tests requiring concentration and executive functions, suggesting a relationship to frontal lobe disease. Bradykinesia in Alzheimer's disease differs quantitatively from the effects of normal aging on movement. Motor function can be reliably measured in Alzheimer's disease patients by simple and rapid tests of tapping speed, which may be useful as functional parameters in studying disease progression and response to pharmacologic intervention.