The Geological Museum in Trinity College Dublin has evolved through the amalgamation of a number of collections and museums of which two, the Dublin University Museum and the Museum of the Geological Society of Dublin, are the most important. Its history may be conveniently divided into three periods: 1, origins and the Dublin University Museum (1777-1857): 2, the Geological Museum in Deane and Woodward's Museum Building (1857-1956); and 3, the Geological Museum in modem times (1956-1990). These three stages, together with the acquisition of certain collections, are outlined below; the major collections of the Geological Museum, its present use, displays, and acquisition policies, are also summarised.