BACKGROUND: ChatGPT has quickly gained popularity as a source of online health information (OHI). However, it is unclear how having a usual source of primary care (USPC) is related to OHI-seeking. OBJECTIVE: Explore how having a USPC and other characteristics thought to affect access-to-care influence the use of ChatGPT and other OHI forms. DESIGN: Cross-sectional national survey. PARTICIPANTS: Adult members of ResearchMatch, a non-profit affiliate of the National Institutes of Health, between June and August 2023. MAIN MEASURES: The survey evaluated demographics, health characteristics, and OHI-seeking behaviors, including ChatGPT usage. OHI sources were categorized as "passive" (Google, Wikipedia, WebMD) and "interactive" (forums, Q&A sites, ChatGPT). Descriptive statistics, t-tests, and chi-square tests compared users by USPC status. Multiple logistic regression estimated adjusted effects on ChatGPT use. KEY RESULTS: Of 21,499 adults invited to participate in the survey, 2406 (11.2%) responded. Among respondents, 56% reported having a USPC. Those with a USPC, compared to those without, were older, spoke English as their primary language, had higher income, and had more formal education (all p<
.001). Participants with a USPC were more likely to use passive OHI (OR 2.46, 95% CI 1.55-3.90, p<
.001) and less likely to use interactive OHI (OR 0.73, 95% CI 0.60-0.89, p=.002) or ChatGPT (OR 0.56, 95% CI 0.44-0.71, p<
.001). Age over 50 (OR 0.11, 95% CI 0.06-0.20, p<
.001), non-White race (OR 0.51, 95% CI 0.38-0.70, p<
.001), very good or better health (OR 0.71, 95% CI 0.55-0.92, p=.009), and college education (OR 0.61, 95% CI 0.39-0.97, p=.035) were inversely related to ChatGPT use. CONCLUSIONS: In this national survey of patients participating in a clinical research matching service, those with regular primary care access relied less on ChatGPT, suggesting that a personal primary care relationship may attenuate the need or motivation to use AI-derived OHI.