Lynyrd Skynyrd frontman Johnny Van Zant has undergone emergency surgery to have his appendix removed.
Van Zant joined the band in 1987, 23 years after it was formed
Van Zant, 46, was treated at Stanford University Medical Center in Palo Alto, California, on Thursday after reporting pain to a doctor earlier in the day.
He is expected to need a week to recover, forcing the rock group to cancel three US shows over the weekend.
Lynyrd Skynyrd, famed for songs such as Sweet Home Alabama and Freebird, have been through several line-up changes.
Founder member Ronnie Van Zant, brother of Johnny, and later additions Steve Gaines and backup singer Cassie Gaines were killed in a plane crash in Mississippi in 1977.
Manager Ross Schilling said on Thursday that Johnny Van Zant "had been feeling bad the past couple of days".
"He had performances Tuesday and Wednesday and sucked it up last night as far as performing with some pain," said Mr Schilling.
A doctor on Thursday morning determined by ultrasound that the performer's appendix was inflamed and emergency surgery was needed.
The band has cancelled shows in Mountain View and Twentynine Palms, California, on Friday and Saturday, and in Henderson, Nevada, on Sunday.
Van Zant is also not expected to attend Tuesday's Academy of Country Music awards, where he and brother Donnie are nominated as duo of the year for their work as Van Zant.