Ronald F. Webbink Department of Astronomy, University of Illinois, 1002 W. Green St., Urbana, IL 61801
Common envelope evolution is essential to the formation of short-
period binaries with compact components. Conditions for its onset, and estimates
of its outcome are summarized. However, applied to the well-known binaries V471
Tauri and T Coronae Borealis, these conditions lead to serious inconsistencies with
their observed properties.