George Clooney returned to "ER" in a long-awaited appearance that gave the TV show its highest viewership ratings in two years as the show nears its final emergency.

Although barely promoted by NBC, the episode in which Clooney's starred boosted "ER" by 11% to a Nielsen preliminary 3.9 rating for the 18-49 demographic. This gave NBC an average 3.1 rating/8 share for the night, coming in fourth-place behind Fox.

Clooney, who played Dr Doug Ross, was one of several former cast members who agreed to return to the show, set in a Chicago hospital, before it reaches the end of its 15-year run. Clooney, Julianna Margulies, Noah Wyle and Eriq La Salle headlined the cast in the 1990s.

All three appeared on last night’s episode, which continued the cast roll call from the past 15 seasons. Previously, others have returned in the show, including Alex Kingston, Laura Innes and Anthony Edwards.

The "ER" series, set in the emergency room of a fictional Chicago hospital, was in the mid-1990s, the top-rated drama on U.S., but audiences have slipped during recent years. For three years ER was the No 1 show in the US, but it was overtaken in 2000 by programmes such as Survivor and Who Wants to be a Millionaire?, and is now in 49th place in the ratings, with only 8.2 million viewers an episode.

To date, "ER" has grasped a record 122 Emmy nominations, including seven consecutive bids for best drama series (1995-2001). It has won 22 Emmys, including a single win for series in 1996.