Joni Mitchell's famous fans are voicing their support for the folk singer while she is in hospital in Los Angeles.
Harry Potter star Emma Watson said on Twitter: "heard about Joni and haven't been able to concentrate all morning. So hope she's doing ok."
Kiss lead singer Paul Stanley tweeted a recent picture of himself and the Rock and Roll Hall of Famer, telling his followers to send her love and prayers.
Actor Kevin Bacon tweeted that he was "sending good wishes today to one of the finest singing, song-writing, guitar playing artists in history".
Boy George, Billy Idol and Tori Amos were also among the well-wishers.
Mitchell, 71, was found unconscious in her home on Tuesday night and taken to hospital by ambulance. Her website said she was in intensive care and undergoing tests.
Mitchell told Billboard magazine last year that she has a rare skin condition, Morgellons disease, which prevents her from performing.
A native Canadian who became part of Southern California's flourishing folk-rock scene in the 1960s, Mitchell has won eight Grammy Awards, including a lifetime achievement award in 2002.
She was inducted into the Rock and Roll Hall of Fame in 1997.