Entered fandom in 1957 and began publishing the Hugo Award-winning fanzine Amra. He chaired the Discon, the Worldcon, in 1963 and wrote the extensive Discon 1 Report on how to run a mid-60s Worldcon. In 1969, he published his first short story in If. Scithers founded Owlswick Press in 1973, and four years later was named the first editor of Isaac Asimov's Science Fiction Magazine, which he left in 1986. Two years later, along with John Betancourt, Scithers re-established Weird Tales. He was the fan guest of honor at Millennium Philcon, the Worldcon, in 2001.
He received a total of four Hugo Awards (the 1964 Best Fanzine Hugo, the 1968 Best Fanzine Hugo, 1978 Best Professional Editor Hugo and the 1980 Best Professional Editor Hugo as well as nominations for the 1962 Best Fanzine Hugo, and Best Professional Editor in 1979, 1981, 1982, 1983, and 1985), a World Fantasy Award, and a World Fantasy Lifetime Achievement Award.
