The number of the elderly is thought to increase up to 12 % in the Eastern Savo Hospital District until 2020. According to the uncascaded model of patient discharge from the hospital they are discharged directly to the home. The goal would be that people are able to live at home as long as possible and as much in good health as possible. Even a few days of bed rest will weaken the physical abilities of the elderly. The causes of the functional ablity decrease must be identified and an additional aim of the dis-ease treatment should be the restoration of functional ability to the level preceding the illness. As hospi-talization is shortened, a structural assessment models are emphasized as well as a rehabilitation plan for the outpatient unit. The purpose of this thesis was to develop an assessment model for the functional ability of the elderly for the physiotherapists as they assess the patients at hospital and give guidance to home-based rehabili-tation. The thesis was assigned by the specialized rehabilitation unit of the Easten Savo Hospital District. Our thesis was carried out as a participatory action research cycle within our work community. To as-sess the current state we collected the information by theme interview on how the physiotherapists as-sess functional ability and need for rehabilitation of the elderly at their home. These results were com-pared to the theoretical background. At the end of the development work we had a meeting where a decision of the assassment model and testing of it was made. The thesis resulted in assessment model of the functional ability for the occupatiol use of physiothera-pists. The model includes the criteria for the home-based rehabilitation. It takes into account the causes of admission and background information and includes analysis of the previous functional ability, as-sessment of the current functional ability and a making of a rehabilitation plan. Hence the model covers all analysis and assessments during the entire hospitalization time . Within the model our primary objective turn out to establish the self evaluation critieria for the elderly. The self evaluation would motivate and engage the elderly to their own recovery. Good coping at home is accomplished by the implementation of the rehabilitation plan and taking care of a good follow-up plan. The new employees and students can take advantage of the assessment model during their orien-tation. Our thesis is the beginning of the development of Sosteri home-based rehabilitation.