A voluntary reporting system of adverse drug reactions (ADRs) is fundamental to drug safety surveillance but under-reporting is its major limitation. This bibliographic review sought to assess the influence of personal and professional characteristics on ADR reporting and to identify knowledge and attitudes associated with ADR reporting. A systematic review was conducted using the MEDLINE and EMBASE databases. We included papers that were published in English, French and Spanish, and covered a study population made up of health professionals. In each case, the following data were extracted: study population; workplace; study type; sample size; type of questionnaire; type of scale for measuring knowledge; response rate; personal and professional factors; and knowledge and attitudes (based on Inman's 'seven deadly sins') associated with reporting. Based on a search of computerized databases, we identified a total of 657 papers in MEDLINE and 973 in EMBASE. In all, the review covered 45 papers that fulfilled the inclusion criteria. Medical specialty was the professional characteristic most closely associated with under-reporting in 76% of studies involving physicians. Other factors associated with under-reporting were ignorance (only severe ADRs need to be reported) in 95%; diffidence (fear of appearing ridiculous for reporting merely suspected ADRs) in 72%; lethargy (an amalgam of procrastination, lack of interest or time to find a report card, and other excuses) in 77%; indifference (the one case that an individual doctor might see could not contribute to medical knowledge) and insecurity (it is nearly impossible to determine whether or not a drug is responsible for a particular adverse reaction) in 67%; and complacency (only safe drugs are allowed on the market) in 47% of studies. While personal and professional factors display a weak influence, the knowledge and attitudes of health professionals appear to be strongly related with reporting in a high proportion of studies. This result may have important implications in terms of public health, if knowledge and attitudes are viewed as potentially modifiable factors.