Context: Poor attachment to a primary care provider is often associated with negative effects on patient health care access and outcomes. Some of these patients however have been shown to be low users of the health care system. Knowing the number and type of patients that have uncertain attachment to their primary care provider is an important element in health system planning. Our study examines levels of attachment and explores specific characteristics of this population over time. Objectives: Our objective was to highlight patterns and changes over time in attachment levels. Study Design: We used an updated validated algorithm for defining attachment to a primary care provider in Ontario using population health administration data. With this approach, we took a detailed look at who are the patients that are attached or uncertainly attached to their primary care provider. Detailed background characteristics were examined on these patients by level of attachment (uncertainly, attached and non-user) within specific regions. This involved reporting on these patients and their physician characteristics. Dataset: We used population level data for all patients in the province of Ontario(approx. pop, 14,000,000.) for the period 2008-2018. Outcome Measures: For the 3 categories of attachment, we examined co- morbidity, health care utilization, age, sex, rurality, income, continuity of care metric, ambulatory care sensitive conditions(ACSC), emergency visits, hospitalizations and Canadian Triage and Acuity(CTAS) levels. Results: Background characteristics of uncertainly attached patients over time will be reported. Full results available at presentation. Conclusions: By examining specific changes by region over time, we can ascertain primary care need. This identification of network needs enables the formulation of health care policy to address these needs.