This study examined how disclosures regarding the progress of clinical trials impact firms’ market value. Disclosures were classified according to the characteristics of the clinical trials, and the effects of each type were examined. We collected disclosure data covering 2009 to 2016 on companies listed on the KOSDAQ market in Korea. Effects on stock prices were analyzed using the event study methodology. The analysis found that the progress of clinical trials had a significant impact on stock prices. Clinical phase entry and completion both had significant effects. When progress was classified into three clinical trial phases, only the entry of Phase III and the completion of Phases II and III had significant effects. When progress was classified into domestic and foreign trials, foreign trials showed significant effects. These results should help equity investors and financial officers at pharmaceutical companies make optimal financial decisions.