U2 say Bono is taking medical advice, after he lost his voice during a gig in Berlin last night.
It meant the show had to be cancelled after just a few songs.
In a statement, the other three band members explained: "We're so sorry for tonight's cancellation. Bono was in great form and great voice prior to the show and we were all looking forward to the second night in Berlin, but after a few songs, he suffered a complete loss of voice.
"We don't know what has happened and we're taking medical advice."
They added that they'll offer an update 'very soon'.
The concert was just the second date of their European tour - they are due to perform four homecoming gigs at Dublin's 3Arena in November.
This is some of the reaction online:
#u2 called off concert early. #Bono said that he's not quite sure what's happened— John Puthenpurackal (@John_BILDde) September 1, 2018
. "I think it's the smoke. I can promise you I have not been talking, but this is like a giant cigar - I've lost my voice and I don't know what to do."#u2gig #berlin
Heartbreak for Bono as he loses his voice and U2 have to cancel the show. But the fans singing Red Flag Day and filling in for the singer is what makes U2 fans among the best in the world https://t.co/UvcHo6x9cv— David Alter (@dalter) September 2, 2018