Since early in 1960 Dr. W. B. N. Berry and I have been actively engaged in synthesizing the available information concerning stratigraphic correlation, lithofacies and pa-leogeography for the Silurian System. Manuscripts dealing with the System for both North and South America have been accepted by The Geological Society of America for publication. First drafts, and in some instances even fourth drafts, have been prepared for the other continents. All of this work has been done with the active collaboration and friendly assistance everywhere of geologists and paleontologists interested in Silurian problems. Berry and I have a personal familiarity in the field with much of the North American, European, and Australian Silurian, as well as a portion of the Near East and Southeast Asia. In addition, we have had the opportunity of dealing with very extensive collections of South American Silurian fossils. With this information in mind, it is obvious that I was happy to have the opportunity under the Cultural Exchange Agreement to make a six months' visit to the Soviet Union with the avowed purpose of examining as much of their Silurian as possible. The chance to check in the field on the lithofacies and paleogeographic concepts developed entirely from the literature and largely at variance with current Soviet concepts, was an attractive one. Unfortunately, however, permission for the farflung travel within the Soviet Union to really “sample” the System was not granted in actual practice despite the terms of the original agreement between the Soviet Academy of Science and our National Academy of Science. However, brief visits to Silurian exposures in Estonia, Podolia, the southwest Urals in Bashkiria, Uzbekistan, and the Altai Mountains gave valuable insights. These insights, combined with the examination of specimens, both fossil and lithologic from most of the Soviet Silurian, and extended discussions with a number of Soviet geologists and paleontologists have been very useful in forwarding our knowledge and synthesis of the System. The following paragraphs will record the outstanding impressions; some substantiate previous conclusions, but others entail serious modifications and emendations.