The research presented in this paper studied the impact selected Information System and Technology (IST) investment announcements had on the market value of firms. It applies the event study method, a method to measure how a company’s share price reacts to new information, to a list of publicly traded Australian firms. It uses and explicitly describes its approach to the selection of a reliable sample and the calculation of share return, which is well-known in financial research, but not established in IS research On this background a total of 62 announcements related to the launching of new IST products or initiatives were selected over 1996 to 2003. On a whole the research showed that these announcements yielded positive abnormal returns only on -1 to +2 days from the announcement dates, the other days in the event window -15 to +15 yielded negative abnormal returns. The results indicate a possible market reaction, but they were not found to be statistically significant. This, in line with previous studies, supports and extends the claim that IST investments have not resulted in increased market value for publicly traded firms not only in the United States, but also in other developed, western countries such as Australia.