This study was designed to estimate the changes of different activities (going to bed, getting up, visiting washroom) of elderly as an index of mobility. The different values in time and number of the different activities were obtained from 16 elderly suffering from Alzheimer’s disease in a hospital for short period observation adding up 4 months of observation data. Significant agreement in different activities (going to bed, getting up, visiting washroom, wandering) among the two measurements by multisensor system and by nursing staff notation was found. As interesting results, the follow up of a patient is shown for 13 consecutive nights. These studies show the potential usefulness of assessment of night activities as an index of mobility, mirror of motor behaviour. Due to minor error, the precise mobility index could not be observed, motor behaviour could simply be evaluated.