'The Big Bang Theory' stars have signed new $1 million-per-episode deals.

Kaley Cuoco, Jim Parsons and Johnny Galecki, who earn a reported $325,000 per episode, have put pen to paper on new contracts with studio WBTV for the next three series of the sitcom leading up to its tenth season.

Sources told The Hollywood Reporter that the trio, Jim - who plays Sheldon Cooper - Johnny (Dr. Leonard Hofstadter) and Kaley (Penny), have agreed $1 million per half-hour deals with added benefits, which could see the stars net a total of $90 million.

However, their co-stars Simon Helberg (Howard Wolowitz) and Kunal Nayyar (Raj Koothrappali) are yet to sign their new contracts, but are expected to have agreed their deals by the end of the week.

Meanwhile, production for the eighth season was delayed by a week last month after the stars refused to start filming until their new contracts had been agreed.

Last month, it was reported the trio were locked in a bitter battle with Warner Bros. after refusing to sign their contracts until they received $1 million an episode.