Health system accountability and the capacity to care for the elderly with increasingly complex care needs is a challenge across many jurisdictions. The move to increasing accountability has necessitated greater and improved measurement of healthcare processes and outcomes. In 2005, the response by the Ontario Ministry of Health and Long-Term Care was to implement the Resident Assessment Instrument (RAI)-Minimum Data Set (MDS) 2.0. One purpose for the introduction of the assessment tool was to facilitate the transition to a new Casemix grouper with associated weights. In long-term care in Ontario, homes are funded based on an envelope system. The majority of expenses related to resident care are provided for in the Nursing and Personal Care (NPC) envelope, which is 100% adjusted for resident acuity. The NPC envelope represents approximately 60% of envelope funding in the sector. Since 1993, this adjustment was based on the Alberta Resident Classification System (ARCS). Assessors from the Ministry measured ARCS once a year and, from these data, residents were classified into one of seven Casemix groups to formulate the province’s Casemix measurement. Long-term care (LTC) homes are funded based on their specific Casemix measure relative to the provincial Casemix measure. Over time the validity of ARCS, and the ability to fairly and equitably distribute funding based on it, came into question. The introduction of the RAI-MDS 2.0, and the Casemix grouping algorithms associated with it, provided alternatives in order to improve the allocation of funding based on Casemix. In collaboration with sector representatives, the Ministry determined that the Resource Utilization Groups (RUGs) 34-group model was best suited to Casemix-adjusted activity in long-term care. A transition model was developed and implemented in order to ensure system stability.