The magazine changed its title several times. It became Marvel Tales in December, 1939, then Marvel Stories in November, 1940. The title reverted to Marvel Science Stories in February, 1951, and then finally to Marvel Science Fiction in August, 1951. Daniel Keyes was associate editor from February to November, 1951, at which time the magazine was published in digest format.
Genre historians seem to agree that the issues published with Keyes as associate editor were superior to other issues. The digest format also made the magazine more competitive with the other digest magazines being published at the time. Authors whose stories appeared during this period included Jack Vance, Betsy Curtis, Ray Bradbury, A. E. van Vogt, Isaac Asimov, Richard Matheson, Murray Leinster, and Raymond F. Jones, with artwork by Hannes Bok, Harry Harrison, and Frank R. Paul. The Bok covers were especially memorable.
In addition, each issue during this period carried entertaining non-fiction departments with contributions from SF personalities such as Judith Merril, Willy Ley, Lester Del Rey, Theodore Sturgeon, Fritz Leiber, Fletcher Pratt, and William Tenn.