Objectives: To assess academic physicians' understanding and usage of basic epidemiological terms commonly used in medical journals. Study Design and Setting: Observational study. A total of 274 physicians, working in a teaching hospital in Paris, France were asked to answer a questionnaire including four vignettes presenting the results of a therapeutic, a diagnostic, a prognostic study and a meta-analysis of clinical trials. Results: A total of 130 (47%) questionnaires were returned. We observed the highest proportion of good answers for questions about absolute risk reduction (87.7%), sensitivity (84.6%), and specificity (80%); and the lowest for the calculation and use of the likelihood ratio (16.9% and 9.2%, respectively). The global mean score was 5.0/10 (95% confidence interval54.6e5.4, range 0e9.4). Physicians got higher scores for questions related to treatment than for questions related to diagnosis: mean scores 7.1 (6.6e7.6) vs. 4.2 (3.8e4.6). Regression analysis did not reveal any significant relationship between global performance and physicians' age (r250.002, not significant [NS]). Conclusion: Physicians demonstrated only moderate knowledge and usage of clinical epidemiology terms used in major medical journals. Their capacity to interpret quantitative data from medical scientific literature may be limited. [Authors]