Adverse drug reactions are a major public health problem. Underreporting is an important limitation of all reporting systems, partially due to attitudes of health professionals.This study sought: (1) to evaluate the reproducibility of a questionnaire on attitudes to and knowledge of adverse drug reaction (ADR) reporting among physicians, nurses and pharmacists: and (2) to compare the attitudes and knowledge of these three groups of health professionals.This study targeted a sample of physicians (n = 30), nurses (n = 30) and pharmacists (n = 20) in the central region of Portugal. A structured questionnaire was administered to each health professional twice, at an interval of 2-4 weeks. Most attitudes were based on Inman's 'seven deadly sins' and measured using a continuous visual analog scale (VAS), with answers scored from 0 (total disagreement) to 10 (total agreement). Questionnaire reproducibility was determined using the intraclass correlation coefficient (ICC).The response rate was 100 %. Attitudes that registered the highest ICCs were Complacency (the belief that really serious ADRs are well documented by the time a drug is marketed) (physicians, ICC 0.84; nurses, ICC 0.70; pharmacists, ICC 0.99), and Diffidence (the belief that one would only report an ADR if one were sure that it was related to the use of a particular drug) (physicians, ICC 0.73; nurses, ICC 0.65; pharmacists, ICC 0.98). In most cases, there were no differences among the three groups of professionals in terms of attitudes and knowledge.The Horizontal continuous VAS is reliable to detect the knowledge and attitudes about ADRs.