Abstract. Icons and symbols are often deployed in graphical user interfaces. It is commonly believed that icons add to the user friendliness of products. Developers have great trust in icon libraries and they are likely to use icons they understand themselves without verifying users' understanding. Interfaces relying on icons that are misinterpreted can lead to erroneous operation. In this study a set of icons in the public domain was interpreted by 64 participants to assess how well general icons are understood. Of the 105 icons included only 67 were correctly identified by all the raters. The results confirm that some basic icons are universally known. However, nearly half of the icons where not identified by all. Recognition correlated with gender, as males were more likely to identify icons connected to masculine concepts and females were more likely to recognize icons connected to feminine concepts. Moreover, a positive correlation was found between the age of the participants and icons depicting ideas from the past versus timeless icons. The results thus support the practice of user testing of icons rather than relying on assumptions.