If was published from 1952 until 1974. The placement and appearance of the "Worlds of" and "Science Fiction" elements changed frequently, such that it was possible to believe the name was 'IF Worlds of Science Fiction', 'Worlds of IF Science Fiction', 'Worlds of IF' or 'IF Science Fiction'. The title itself was unique enough that this hardly matters.

The British edition went through numerous incarnations: the first run lasted from 1953 until 1955. It was then resurrected from 1959 until 1962, again for several issues in 1967, once more from 1969 until 1970 and its final run lasted from 1972 until 1974.

Worlds of Tomorrow was published from 1963 until 1967, when it was combined with IF as IF Worlds of Science Fiction Combined with Worlds of Tomorrow. It was then briefly resurrected under its own name for several issues between 1970 and 1971.

The World of If Reader and Best Science Fiction From Worlds of If were anthology reprints published in digest size.