To assess the reliability and validity of a subset of the Minimum Data Set (MDS) 3.0 Section GG data elements (i.e., standardized self-care, mobility) among 147 long-stay nursing home residents in seven nursing homes in five states. Trained clinicians assessed residents' functional abilities using select Section GG items and Section G activities of daily living items. We examined the reliability and construct validity of the data using Cronbach's alpha, correlations between Section G and Section GG items, confirmatory factor analysis (CFA), and Rasch measurement analysis. We observed acceptable internal consistency values for all (0.98), self-care (0.93), and mobility (0.98) standardized items. Correlations between conceptually related Section G and Section GG items ranged from -0.53 to -0.84. CFA findings found acceptable values for all fit indices. Rasch analysis showed most items had acceptable fit statistics, except for the easiest and most difficult activities. These findings establish the feasibility of data collection, internal consistency reliability, and construct validity of the selected Section GG items among long-stay nursing home residents. Use of the same standardized data elements in post-acute and long-term care populations can support improved coding of function and enhance our understanding of resident functioning. [Research in Gerontological Nursing, 17(2), 57-64.].