Background:Few studies have evaluated the continuity of primary care in universal health care systems, especially in underserved areas.Methods:This was a cross-sectional study with 4,001 adults (≥18 years old) living in the Manaus Metropolitan Region in 2015. Interviews were conducted in households selected with probabilistic sampling. City and neighborhood variables were collected from databanks. Prevalence ratios (PR) of the continuity of care (defined as using a primary care service and having been previously registered in the Family Health Strategy program) and 95% confidence intervals (CIs) were calculated with multilevel Poisson regression analysis.Results:A total of 20.6% (95%CI 19.4-21.9%) of the participants reported continuity of primary care. Women (PR = 1.38; 95%CI 1.18-1.61), nonwhite individuals (PR = 1.13; 95%CI 1.05-1.21), and poorer people (PR = 1.55; 95%CI 1.19-2.02) had higher levels of continuity, whereas health insurance holders had lower levels of continuity (PR = 0.46; 95%CI 0.34-0.62). Individuals with continuity of care had more physician consultations (PR = 1.06; 95%CI 1.02-1.10), dentist consultations (PR = 1.16; 95%CI 1.05-1.28), fewer depressive (PR = 0.59; 95%CI 0.44-0.79) and anxiety symptoms (PR = 0.64; 95%CI 0.48-0.85), and a higher quality of life (β = 0.033; 95%CI 0.011-0.054) than those without continuity.Conclusions:Continuity of care was attained by two-tenths of the population and the level of continuity was high among socioeconomically disadvantaged people. Good outcomes and health services usage increased with continuity of care.