According to the efficient market hypothesis the stock price for a company should be evoked immediately when new and unpredicted information about the company’s value is published. A publishing of a qualified audit opinion that disclose previously unknown negative aspects of a limited liability company, should thus result in a negative impact on its share price. Previous studies in the field, on the other hand, show conflicting results. In some cases, a negative impact has been found, in other cases a positive impact has been found while in some cases no impact could be observed. The study's selection framework consists of 223 Swedish listed limited companies which have received a qualified audit opinion during the fiscal years 2011-2018. A stratified random sample was made where 142 companies were examined. This study aims to examine what relationship can be found between an audit opinion and abnormal returns for the company's share. Abnormal returns indicate the difference between expected returns and observed returns. The study is performed according to an event study with event windows of three different extents, from 1 day up to 21 days. The abnormal return on the shares has been studied according to the Market model. The results of the study are in line with previous research and show conflicting results. Over event windows of 21 days and 3 days, the majority shows a positive abnormal return and in contrast, the majority shows a negative abnormal return in terms of the event day only. It can be stated that investors on the Stockholm Stock Exchange react negatively only to going concern opinions. The results may further indicate that the Swedish market is efficient where reactions to new information in auditor opinions are immediate, rather than over time. The results may also indicate that investors are not the primary stakeholders to which the auditing profession should be adapted to in Sweden.