Best won 23 caps for Ireland
Ireland and Ulster prop Simon Best has announced his retirement from rugby.
The forward, 30, was advised to quit on medical grounds after being diagnosed with an irregular heartbeat following a health scare during the World Cup.
"It is with great sadness that I am forced to retire at this stage in my career," said Best, who won 23 caps.
"I have no regrets and feel immensely proud and privileged to have represented both Ulster and Ireland for the past nine years."
Best, who is the brother of the Ireland hooker Rory, was taken ill while on a visit to Bordeaux and rushed to hospital after developing a loss of sensation down his right side.
He was an incredibly honest, talented and hard working player in every aspect of his participation in the game and a model professional
Ireland coach Eddie O'Sullivan
He has suffered no further health problems, but his medical experts have advised against resuming the intense levels of training and playing required for a professional career in rugby union.
"I am grateful to have had the opportunity to work with coaches, management and players that I have had the utmost respect for and have formed lifelong friendships with many," he added.
"I would like to thank the Ulster and Ireland supporters and my friends and family for their loyalty and support throughout my career and during this difficult time.
"I would also like to take this opportunity to thank the IRFU and their medical team for the extremely high standard of care that I have received.
SIMON BEST FACTFILE
Born: Craigavon, 11 Feb 1978
Teams: Belfast Harlequins, Ulster, Ireland
Caps: Ireland (23), Ulster (118)
Debut: v Tonga 14 June 2003
"Finally, having grown up as a supporter of Ulster and Irish rugby I would like to wish the players and management of both squads all the very best for the rest of the season and the coming years.
"I will continue to support and follow their future successes with great interest."
Best played 124 times for Ulster and twice skippered Ireland, leading them on their two-match trip to Argentina last summer.
"He was an incredibly honest, talented and hard working player in every aspect of his participation in the game and a model professional," said Ireland coach Eddie O'Sullivan.
"In addition to that, he was and still is an extremely popular guy with all the players and it is very unfortunate that his career has been cut short by this condition when he still had so much more to offer Irish rugby."
Best made his international debut against Tonga in June 2003 and his first start against Wales in August of the same year.
His last game was a replacement in the World Cup defeat by hosts France last September.
Best, who was educated at Portadown College, also represented Ireland at Schools, U19, U21, U25 and A levels.