A Ralph Edwards production, it was hosted by Arte Johnson, with announcing duties handled first by Jay Stewart and later by John Harlan.
A new list was played whenever any of the following occurred: A player could earn up to six letters in one turn by choosing the unrelated item, successfully daring both opponents, and then guessing the category.
In the first half, the champion was shown a list of three items, one at a time, and tried to guess the category to which they belonged after each was revealed.
Succeeding Monty Hall's short-lived It's Anybody's Guess, Knockout marked Ralph Edwards' third attempt at a daytime game on NBC in as many years.
After failing with two different short-lived versions of Name That Tune on NBC daytime, which had become a major hit off network, he banked on the appeal of former Laugh-In star Johnson who had, in the intervening years since that show's cancellation, become a regular panelist on games like Hollywood Squares and Gong Show.