Season 1

Season 1 of The Avengers premiered on January 7, 1961

"Girl on the Trapeze," "The Frighteners," "Tunnel of Fear" and the first act of "Hot Snow" are the episodes known to exist of the first series.

Season 2

Season 2 of The Avengers premiered on September 29, 1962

Season 3

Season 3 of The Avengers premiered on September 28, 1963

Season 4

Season 4 of The Avengers premiered on October 2, 1965

Season 5

Season 5 of The Avengers premiered on January 14, 1967

Season 6

Season 6 of The Avengers premiered on September 25, 1968