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More than 7 million people are released each year from U.S. jails or prisons, many with chronic diseases that would benefit from primary care in their returning communities. The objective of this study was to provide an in-depth, payer-agnostic description and associational analysis of primary care need and utilization by all individuals ever detained in one county detention facility over a 7-year period. Detention records 2014–2020 were merged with data from an electronic health record with excellent coverage of local primary care, emergency, and hospital services. We found low primary care participation for the group as a whole, with under three quarters of those with serious chronic diseases ever seeing a primary care provider over a 7-year period and less than half ever having a year with more than one visit. Multivariable regression models estimated associations between individual characteristics (demographic, detention-related, and clinical) and ever having access to primary care (logistic) and the number of primary care visits (zero-inflated negative binomial). We found that having more jail bookings was associated with fewer primary care visits, but not one-time access, even controlling for time out of community, age, insurance, and other demographic characteristics. This finding was driven by subgroups with chronic disease such as hypertension, obstructive lung disease, and diabetes, who most need regular primary care. Being Black retained an independent effect, even controlling for bookings and other variables, and was also associated with fewer primary care visits, though not one-time access. To promote primary care utilization among individuals who have the combined challenges of repeated jail involvement and chronic disease, it is crucial to focus on engagement, as much as formal access. Access to health insurance alone will not resolve the problem; Medicaid expansion should be coupled with specialized, tailored support to promote engagement in primary care.