Amy Mickelson had surgery for breast cancer on 1 July
World number two Phil Mickelson has withdrawn from the Open at Turnberry to be with his wife and mother as they both battle breast cancer.
His wife Amy had surgery on 1 July and is awaiting more test results.
Mickelson said: "Competing in major championships, and winning them, is my main objective. But I've always said family is my number one priority.
"For that reason I won't be playing the Open," added the American, who is optimistic about his wife's recovery.
Three-time major winner Mickelson will be replaced in the field by fellow American Ben Crane.
"It's a trying time for us but we have excellent medical attention and care," said Mickelson.
"We've received wonderful support from so many people, many of whom have gone through the same battle, and we're optimistic, as always."
The 39-year-old has played the last 61 majors, the longest active streak in golf.
He has contested every Open since he turned professional in 1994, but only finished in the top 10 once when he was third at Troon in 2004.
Mickelson returned from a break to finish second at last month's US Open for a record fifth time, subsquently revealing that that event would probably be his last competitive outing until August.
The Open gets under way in Turnberry on Thursday 16 July.