US pulp science fiction and fantasy magazine, which ran from 1952 until 1974. During the 1950s, it occasionally carried the subtitle Worlds of Science Fiction. The magazine ran through a number of editors, but experienced its greatest success during the seven years (1962 to 1969) when it was edited by Frederick Pohl, during which time it won three consecutive Hugo Awards for best professional magazine (1966 to 1968). After the Nov./Dec. 1974 issue, the publishing house decided that rising publication costs made it impractical to continue publishing both If and their other science-fiction magazine, Galaxy: If was merged with Galaxy.