This study discussed the determinants and market impacts of open and closed conference calls. Since there were no explicit indicators for open and closed calls in Taiwan, we used two criteria to separate calls into open (public) and closed (private) ones. The first criterion was whether the call provided video records on the company’s website or Market Observation Post System (MOPS). The other was whether the convention of the conference call was announced at least 3 days before the events. First, we adopted an event study and verified that conference calls in 2014 provided incremental information. Then, we applied logit models to analyze the determinants of holding different types of calls. We discovered that companies with more shareholders (LNOWN), higher BP ratio (BP), more intangible assets (INTAN), a smaller number of employees (LNEMP), larger market value (LMV), less public listing time (LTIME), and in hi-tech industries (DTECH) were more likely to convene open calls. In the last part of this study, we used the univariate analysis to compare the market changes before and after open and closed calls. We found out that open calls would lead to more increase of non-institutional trades and larger stock-trading volume than closed calls.