We have recently developed a health monitoring system for the elderly living alone. We measured in-house movements by placing infrared sensors in each room of their houses without restricting them so that monitoring can last longer. Continuous monitoring was performed for 91 months in total to 8 subjects. We estimate their health condition by checking the staying periods at specific rooms such as a lavatory in comparison with the previous data statistically. If there is a unusual state after analysis, we have to inform the family of the incident. Final decision should be made by their family. After inquiring with the subject or his/her neighbors by telephone, family members may call an ambulance, if necessary.