BACKGROUND: Individuals with limited English proficiency experience poor patient-clinician communication. Most studies of language concordance have not measured clinician non-English-language proficiency. OBJECTIVES: To evaluate the accuracy of the self-assessment of non-English-language proficiency by clinicians compared with an oral proficiency interview. SUBJECTS: Primary care providers (PCPs) in California and Massachusetts. MEASURES: PCPs first completed a self-assessment of non-English-language proficiency using a version of the Interagency Language Roundtable (ILR) Scale, followed by the Clinician Cultural and Linguistic Assessment (CCLA), a validated oral proficiency interview. We used nonparametric approaches to analyze CCLA scores at each ILR scale level and the correlation between CCLA and ILR scale scores. RESULTS: Sixteen PCPs in California and 51 in Massachusetts participated (n=67). Participants spoke Spanish (79%), followed by Cantonese, Mandarin, French, Portuguese, and Vietnamese. The respondents self-assessed as having "excellent" proficiency 9% of the time, "very good" proficiency 24% of the time, "good" proficiency 46% of the time, "fair" proficiency 18% of the time, and "poor" proficiency 3% of the time. The average CCLA score was 76/100. There was a positive correlation between self-reported ILR scale and CCLA score (sigma=0.49, P < 0.001). The variance in CCLA scores was wider in the middle categories than in the low or high ILR categories (P=0.003). CONCLUSIONS: Self-assessment of non-English-language proficiency using the ILR correlates to tested language proficiency, particularly on the low and high ends of the scale. Participants who self-assess in the middle of the scale may require additional testing. Further research needs to be conducted to identify the characteristics of PCP whose self-assessments are inaccurate and, thus, require proficiency testing.