When attempting to select the important American productions of the plays of Eugene O'Neill, I was struck by the unavoidable conflicting views of what should make a production of a play significant in presenting a capsule stage history of the work of one of our most enduring playwrights. How important are the first productions of a play compared to revivals since the production personnel were the first to attempt to solve the problems of the plays? Yet some later efforts were clearly more finished or exciting. Furthermore, if a first production occurred while O'Neill was still living he often participated in production. And what of plays which are revived professionally nearly every year, like Long Day's Journey Into Night or Ah, Wilderness! versus important but only occasionally revived plays like Anna Christie or The Great God Brown? What of popularity versus critical approval? And what of the literary value of the play? Is a clear but uninspiring production of Mourning Becomes Electra more important than a fascinating interpretation of Welded?