This article reports on the results of an unobtrusive study used to measure whether online chat reference can effectively answer short, subject-based research questions. The University of Illinois Ask a Librarian virtual reference service is run from the regular reference desks of the Main Reference Library and Undergraduate Library, two of the more than forty departmental libraries on campus. The unobtrusive study took place during April 2003. For the period of the survey, there were 856 total chats received. Proxies were trained in using the chat software from both the patron end as well as the staff side, and instructed to try a few sample questions on their own before asking the actual study questions. Complete or ideal transactions were recorded for 47 percent of the reference encounters, with Mostly Complete transactions accounting for another 32 percent. The average duration for all the chats was fifteen minutes, fourteen seconds. The transactions ranged from four minutes to thirty-three minutes in length. One important trend was that the less complete a chat, the longer the average duration. A breakdown of chat duration by the types of sources used shows that asking for two books has the shortest duration, asking for two articles averages fifteen minutes and forty-four seconds, and asking for one book and one article takes the longest at sixteen minutes and twelve seconds.