BACKGROUND: Black Americans and women report feeling doubted or dismissed by health professionals. OBJECTIVE: To identify linguistic mechanisms by which physicians communicate disbelief of patients in medical records and then to explore racial and gender differences in the use of such language. DESIGN: Cross-sectional. SETTING/PARTICIPANTS: All notes for patients seen in an academic ambulatory internal medicine practice in 2017. MAIN MEASURES: A content analysis of 600 clinic notes revealed three linguistic features suggesting disbelief: (1) quotes (e.g., had a "reaction" to the medication); (2) specific "judgment words" that suggest doubt (e.g., "claims" or "insists"); and (3) evidentials, a sentence construction in which patients' symptoms or experience is reported as hearsay. We used natural language processing to evaluate the prevalence of these features in the remaining notes and tested differences by race and gender, using mixedeffects regression to account for clustering of notes within patients and providers. KEY RESULTS: Our sample included 9251 notes written by 165 physicians about 3374 unique patients. Most patients were identified as Black (74%) and female (58%). Notes written about Black patients had higher odds of containing at least one quote (OR 1.48, 95% CI 1.20-1.83) and at least one judgment word (OR 1.25, 95% CI 1.02-1.53), and used more evidentials (β 0.32, 95% CI 0.17-0.47), compared to notes of White patients. Notes about female vs. male patients did not differ in terms of judgment words or evidentials but had a higher odds of containing at least one quote (OR 1.22, 95% CI 1.05-1.44). CONCLUSIONS: Black patients may be subject to systematic bias in physicians' perceptions of their credibility, a form of testimonial injustice. This is another potential mechanism for racial disparities in healthcare quality that should be further investigated and addressed.