In 1956, the production of Long Day's Journey into Night by the Royal Dramatic Theatre in Sweden won much praise for O'Neill. Potential producers soon pressured Carlotta O'Neill to release the work for an American staging, and after several months she turned the play over to Jose Quintero and two associates. Quintero's earlier revival of The Iceman Cometh, which opened in May of 1956, had already prompted new enthusiasm for O'Neill. His New York production of Long Day's Journey into Night, coupled with the play's publication by the Yale University Press, fully elevated O'Neill's reputation and restored him to the front ranks of American dramatists.

Leading critics like Brooks Atkinson, Walter Kerr, Harold Clurman, and Joseph Wood Krutch proclaimed the play's power on stage. Kerr, for example, in his review in the New York Herald Tribune, called the play "a stunning theatrical experience," while New York Times critic Atkinson announced that with the production of Long Day's Journey into Night the American theater had reached "stature and size." But the critical vindication of O'Neill was not unanimous. Some reviewers subtly condemned the work with tepid praise. Others pondered the play's stage power in the face of what Stephen Whicher, reviewing the Stockholm production for Commonweal, claimed were "several massive faults which should have destroyed it." Yet others paraded out old complaints about the playwright's heavy handed, awkward technique, tortured dialogue, painful self-flagellation, oppressive length, and morbid pessimism. One reviewer, Gilbert Seldes, commenting on the published play in Saturday Review, faulted the playwright's repetition, long speeches, "passion for reciting poetry," and his "desperate flatness of language." Another commentator, the New Yorker's Wolcott Gibbs, complained that the play "is often as barbarously written as it is possible for the work of a major writer to be," and doubted the work's status "as a major contribution to the drama of our time."

The unabashed autobiographical content of Long Day's Journey into Night also troubled many critics, some of whom argued that the play simply failed to evoke the emotions appropriate to tragedy because, as C. J. Rolo maintained in the Atlantic Monthly, the characters were "not only devoid of heroic attributes" but "even lacking in ordinary dignity and strength." For Rolo, the play failed to produce what O'Neill himself referred to as the "transfiguring nobility of tragedy."

Artistically, O'Neill, a tireless innovator, always had to swim against some pretty strong critical currents. Noting what seem like obvious flaws in his work, some important critics have only grudgingly agreed to O'Neill's status as the dean American theater. There is, for example, Eric Bentley's famous quip: "He is the leading American playwright; damn him, damn all; and damning all is a big responsibility." Bentley's frustration with O'Neill partly stems from what has always bedeviled O'Neill's critics—the fact that his texts never seem to suggest the grandeur that their dramatizations often achieve on stage. Away from the magic of theater, under a reader's naked light, his plays can sometimes seem pedestrian and awkward, almost embarrassingly so.

That fact has made some writers circumspect in approaching O'Neill's published plays. Harold Clurman, reviewing the Yale text of Long Day's Journey into Night in the Nation, remarked that "O'Neill's plays are nearly always more impressive on the stage than on the printed page." O'Neill was "a faulty craftsman," perhaps, but, as Clurman noted, the Swedish production had held its audience transfixed for four and one-half hours, a performance length that modern audiences would normally find unendurable, barely tolerable in a great classic like Shakespeare's Hamlet , which litters the stage with...