The final ever episode of US medical drama ER was watched by an estimated 16.4 million people. It was the biggest audience for the final show of a drama since Murder she Wrote on CBS ended in 1996, Nielsen Media Research said.
Former stars Noah Wyle and Eriq La Salle appeared alongside the current cast in the two-hour finale.
A fortnight ago, George Clooney returned for a brief cameo in the NBC show, which ran for 15 years.
The audience was up from average weekly figures for the season of 9.5 million.
But ratings for the finale were still half of the show's average audience of 32 million viewers in 1995, when it was the most watched show on US television.
The final episode of the show, set in the emergency room of a fictional Chicago hospital, was written by former producer John Wells.
Clooney, 47, left the show in 1999 to pursue a film career and, in 2005, won an Oscar for best supporting actor in thriller Syriana.
The new Clooney episode will be shown in the UK on More4 on 14 May, while the final episode will be screened on 4 June.
BBC NEWS | Entertainment | ER finale pulls in 16.4m viewers
ER finale pulls in 16.4m viewers
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