The inquired disclosure is a system operated by the Korea Exchange (KRX) to validate the existence of material information when the price of a listed stock fluctuates substantially. It is different from other timely disclosure since KRX inquires information, and the firm confirms the information inquired by the Exchange whereas in case of other timely disclosure the firm itself mandatorily or voluntarily release information to the investors. According to the efficient market hypothesis, the stock prices react only to new fundamental information. Sometimes, the stock prices exhibit noticeable jump or plunge without any specific public information. In that case, the Exchange inquires of the firm about the reason for the noticeable price changes. In response to the inquiry from the Exchange, the firm usually provides two types of answers such as “nothing unusual” or “something undetermined.” This paper investigates how the demand for inquired disclosure from the Korea Exchange affects the movements of stock price and trading volume for the period of ±20 days surrounding the event. The event date is defined as the day when the Exchange demands the inquired disclosure related to the stock price jump or plunge occurring without any specific public information. Also, this paper investigates the trading patterns of different investors (classified as individual, institutional, and foreign investors) surrounding the day of inquiry. For this purpose this paper examines the cases of the KOSPI-listed firms which are inquired to be disclosed for the explanation of the jump or plunge of stock price for the period from 2005 to 2009. We collected a total of 497 samples which are composed of 436 cases of jump and 61 cases of plunge. Then these samples are divided into four groups depending on price changes and types of firms' answers, such as jump/something undetermined, jump/nothing unusual, plunge/something undetermined, and plunge/nothing unusual. This paper employs typical event study methodology, and computes the abnormal return (AR) and the cumulative abnormal return (CAR) surrounding the event day using the market adjusted return model. The main results and implications drawn from the empirical analysis are as follows. First of all, we find insignificant abnormal return on the day of inquiry followed by stable price movements, suggesting that the demand for inquired disclosure from the Korea Exchange can play an effective role in calming down price jump or plunge. However, we do not find price reversals on the day of inquiry that are expected to exhibit if the past substantial price changes occurring without any specific public information were bubble. In addition, in case of something undetermined we observe 10-day CAR of -6% following the inquiry after plunge and +6% following the inquiry after jump whereas in case of nothing unusual insignificant price changes are observed following the day of inquiry. This result implies that in case of something undetermined stock price continues to reflect new information revealed in the market. Next, in the investigation of long-term stock price movements following the demand for inquired disclosure from the Exchange we find that in the case of plunge the stock prices tend to steadily increase following the day of inquiry. In particular, in case of plunge/nothing unusual the stock prices revert to the past level of stock prices. However, in the case of jump, we do not find any significant patterns of long-term price changes following the inquired disclosure. In this paper we also observe that the trading volume significantly increases during ±5 days surrounding the day of inquired disclosure. This finding suggests that investors are getting more sensitively responsive to the information of the demand for inquired disclosure from the Exchange. Finally, this paper investigates the trading patterns of three different types of investors classified as individuals, institutions, foreigners by observing the ratio of each investors' net buying (selling) position. We find that individual investors are the main driving force behind the stock price jump or plunge as net buyers while the institutions as net sellers. In particular, individual investors take net buying position on the day of inquiry and continue afterwards whereas institutional investors take net selling positions during that period only. On the other hand, foreign investors do not exhibit any notable trading patterns, suggesting that foreign investors do not respond to uncertain information in the Korean stock market. On the whole, this study is to contribute to the academic research in the area of market efficiency and informational effect. In particular, this paper can accelerate the studies on the informational effect of inquired disclosure in the Korean stock market. Also, the evidence of this research is expected to provide useful information to the investors in the stock market who frequently observe substantial price changes occurring without any specific public information. In addition, the empirical results of this study reveal important implication to the policy makers who are interested in the effectiveness of inquired disclosure system.