The aim of the study is to identify, analyze and evaluate changes and trends in the use of collectively created on-line Wikipedia Encyclopedia within the framework of the Czech virtual reference service „Ptejte se knihovny“ (Ask Your Library) (http://www.ptejteseknihovny.cz/). Survey sample consists of the records in the archive of the answered questions from the years of 2003 to 2012 published in a freely accessible on-line archive of the service „Ptejte se knihovny“ (Ask Your Library) (http://www.ptejteseknihovny.cz/archiv) that include references to the Wikipedia entries and also the links to Wikipedia from the all archive records (i.e. regardless of their location in the archive records).
The first step of the survey has been to find out the number of archive records with references to Wikipedia, the number of the references to the encyclopedia and the types of Wikipedia entries. Those records have been analysed using the method of bibliometric citation analysis.
The author publishes the results with her own commentary. The basic hypothesis of the survey states that the extent of use and citing of the Wikipedia data within the service „Ptejte se knihovny“ (Ask Your Library) has been steadily increasing, especially the use of the Czech language version of the encyclopedia, and that the extent of use and citing of other selected major general encyclopaedic works produced in a traditional way (printed or on-line) is substantially lower than that of Wikipedia.
The results of the survey partially affirm increasing use of the Wikipedia as an information and reference source not only by general public, but also by librarians and information officers.