The former BBC darts commentator Sid Waddell has been diagnosed with bowel cancer.
The 71-year old, whose voice has become synonymous with the sport, left the BBC in 1994 to broadcast for Sky Sports.
Waddell thanked fans for their best wishes via Twitter, saying "Bowel cancer's not a barrel of laughs so I'll be switching off from Twitter until things get better."
The Cambridge graduate is also a published author and screenwriter.
Northumberland-born Waddell is well-loved for his colourful and excitable commentary style, with his best-known lines including "There's only one word for it - 'magic darts"'.
He also noted, while watching Eric Bristow become world champion: "When Alexander of Macedonia was 33, he cried salt tears because there were no more worlds to conquer... Bristow's only 27."
A statement from his manager Dick Allix read: "Following recent tests, Sid has unfortunately been diagnosed with bowel cancer. He is now undergoing treatment and will, regretfully, be unable to undertake any professional engagements for the time being.
"As treatment progresses, I will issue further statements. I would ask that everyone respects his privacy at this time."
Professional Darts Corporation chairman Barry Hearn said: "Sid is a hugely popular character throughout the sport of darts and I'm sure I speak on behalf of the PDC, our players and fans in wishing him a speedy and successful recovery.
"Our thoughts will be with him and his family as he begins his treatment."
Waddell, who began commentating on darts in 1978, was inducted in to the PDC Hall of Fame in 2008.
Outside of his commentary work, he has had 11 books published and wrote the sport-based BBC children's programmes Jossy's Giants and Sloggers, receiving a Screenwriter's Guild nomination for best scriptwriter for the latter.