Arrowfield stallion Not A Single Doubt has been retired from active duty and is under veterinary care for pulmonary disease.

The stud said the 18-year-old had shown no improvement despite ongoing treatment.

"He suffers respiratory compromise at rest and even short periods of hand walking exacerbate this," Arrowfield boss John Messara said.

"Our head vet has advised that Not A Single Doubt is incapable of performing his breeding duties and accordingly he has been retired from active service.

"Not A Single Doubt is a wonderful story for Arrowfield and for many breeders, owners, buyers and trainers, rising from the bottom of our roster to become one of Australia's most popular and successful stallions.

"We are immensely grateful to him, and he will be loved and cared for at Arrowfield for the rest of his life."

A first-crop son of champion sire Redoute's Choice, Not A Single Doubt was bred at Arrowfield from Singles Bar, a daughter of Rory's Jester and the celebrated broodmare Easy Date.

Not A Single Doubt is the sire of 69 Group and Listed winners from 1000 to 2600 metres.

He has produced 11 Group One winners so far including Extreme Choice, Kenedna, Miracles Of Life, Scales of Justice, Secret Agenda, Single Gaze and Samadoubt.

Not A Single Doubt was the leading Australian-based sire on worldwide prize money in 2015/16 and is currently third on the Australian 2019/20 two-year-old sires' premiership.

His 32 yearlings sold at the recent Magic Millions sale for an averaged of $344,531.

Not A Single Doubt covered 94 mares in the spring for a career-high fee of $110,000.