OBJECTIVE: To develop and validate an asthma knowledge questionnaire for use in adult asthma patients in Brazil. METHODS: A 34-item self-report questionnaire was constructed and administered to adult asthma patients and adult controls. The maximum total score was 34. RESULTS: The questionnaire was shown to be discriminatory, with good reliability and reproducibility. The mean score for asthma patients and controls was, respectively, 21.47 ± 4.11 (range: 9-31) and 17.27 ± 5.11 (range: 7-28; p <

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... .001). The Kaiser-Meyer-Olkin measure of sampling adequacy was 0.53, and the Bartlett's test of sphericity demonstrated a satisfactory suitability of the data to factor analysis (p < 0.001). There was no significant difference between the total scores obtained in the first and in the second application of the questionnaire within a two-week interval (p = 0.43). The internal consistency reliability (KR-20 coefficient) was 0.69. CONCLUSIONS: This study has validated an asthma knowledge questionnaire for use in Brazil.