Five various functional assessment criteria were applied in this study to estimate the size of non-institutionalized elderly population eligible for long-term care services in Taiwan. The five criteria from the most restrictive to the least restrictive were: (1) three or more ADLs disability, (2) two or more ADLs disability, (3) any ADLs disability, (4) any ADLs or IADLs disability, (5) any ADLs or IADLs or moderate cognitive impairment. Functional evaluation of an islandwide representative sample with 2,892 noninstitutional respondents aged 65 and over showed that the size of the eligible elderly population ranged from about 40,000 persons under the most restrictive disability criterion (human assistance required with three or more ADLs) to 270,000 persons if the least restrictive criterion (instrument or human assistance required with any ADLs, IADLs or moderately cognitive impairment) was applied. The estimate is going to increase 4 times 40 years later. Because the analysis was based on a sample of community elderly, the estimate derived from this study was not including the elderly who have already resided in an institution. The estimate represented the elderly population who were in need of home- or community-based long-term care.