Leading international stallion Street Cry has been euthanised after failing to recover from a rare neurological condition.

The 16-year-old had been ill for some weeks at Darley Stud in the NSW Hunter Valley and the decision to put him down was made late on Wednesday when he suffered complications.

The sire of the 2009 Melbourne Cup winner Shocking, Street Cry was a cornerstone of Sheikh Mohammed's racing and breeding operation in both Australia and the United States.

The runaway winner of the 2002 Dubai World Cup, Street Cry went to stud in Kentucky in 2003. His first crop included future champion Zenyatta and Street Sense, the only horse to win both the Breeders' Cup Juvenile and the Kentucky Derby.

Street Cry has sired 15 Group One winners and almost 150 stakes winners worldwide.

Sheikh Mohammed's bloodstock advisor John Ferguson said Street Cry's death was a huge loss.

"Street Cry epitomised everything that Darley and Godolphin aim to achieve he was bred by Sheikh Mohammed in Ireland, excelled at the very highest level on the racecourse in Dubai and the US, and then became the lynchpin of our stallion operations in both America and Australia," Ferguson said.

"His contribution to the breed has been significant and we have been so fortunate to have him. He will be sorely missed by everyone."

His trainer Saeed bin Suroor said Street Cry was one of his favourites.

"He was a brilliant horse, who was from a superb family and so easy to train," he said on Godolphin's website.

"He proved himself to be one of the world's best, while his progeny have gone on to win many big races all over the globe."