Therapeutic ineffectiveness is a frequent drug-related problem that can occur in a variety of different situations and be caused by different mechanisms. Examples are inappropriate use, interactions or metabolic abnormalities. Observations in patients of unexpected ineffectiveness can provide important information with regard to such situations. Therefore, ineffectiveness--especially when unexpected or unexplained--is a potentially important reportable event in pharmacovigilance. The terms regarding ineffectiveness in the WHO Adverse Reaction Terminology (WHOART) have been recently revised in order to enable optimal coding of such case reports.