Valve has announced that "Half-Life 2: Episode One" has gone gold and will be available on June 1^st.

"Half-Life 2: Episode One advances the 15-million unit selling franchise and launches the first in a new, three-part series that leads far beyond City 17. Half-Life 2: Episode One does not require Half-Life 2 to play, and will be available via Steam® and at retail stores in North America for just $19.95 on June 1st. Also included in Episode One is a first look at Episode Two, which will ship by year's end.

"Given the rapid changes in PC gaming, we expect episodic games will have the same impact on single-player gaming that Counter-Strike had on multiplayer," said Gabe Newell, president and co-founder of Valve. "The frequent releases of upgraded technology and new content works better for both consumers and developers, and is one of the key reasons Counter-Strike grew to be 80% of the online action market. We decided that a follow-up to Half-Life 2 delivered in 18 months with our first episode was more in tune with what our customers want than waiting 6 years for another monolithic product."

Episode One offers a new single player experience created by Valve, and is designed to be four to six hours in length. Stepping into the hazard suit of Dr. Gordon Freeman, you face the immediate repercussions of your actions in City 17 and the Citadel. Alyx Vance and her robot, Dog, will accompany you in your efforts to aid in the human resistance's desperate battle against the totalitarian alien menace of the Combine.

In addition to the new single player experience, two multiplayer games are included. And those who purchase Episode One will have free access via Steam to Half-Life 2: Lost Coast, the interactive technology demo that introduces High Dynamic Range lighting to the Source^TM Engine, Valve's award-winning game technology."

Valve also announced that Episode One is the first in the trilogy which will conclude Christmas of 2007.

Along with this announcement, a new teaser trailer has been released.