Celebration was tainted with upset at the annual Dublin Marathon when a runner collapsed at the finish line.
As the nation claimed its first double win in 20 years, a man was rushed to hospital with a suspected heart attack.
Organisers said the man, believed to be one of the 14,600 competitors in the race, was in serious condition.
"We are very concerned about his wellbeing," said a spokeswoman for the Airtricity Dublin Marathon.
"He was a competitor and he collapsed at the finish line. Members of St John's Ambulance treated him and he was taken to hospital almost immediately."
She said medics confirmed the man had a pulse when he arrived at a nearby hospital, following his collapse shortly after lunchtime.
"We are staying very much in touch with the hospital to keep up to date with how he is doing," she said.
Just hours earlier, Clare man and primary school teacher Sean Hehir won the 26.2 mile race with a time of 2 hours, 18 minutes and 19 seconds.
Maria McCambridge, originally from Donegal, was the fastest woman, crossing the finish line after 2 hours, 38 minutes and 51 seconds.
Theirs is the first double Irish win since John Treacy and Cathy Shum ran to victory in 1993.
The record crowd of competitors turned out for the Airtricity-sponsored marathon despite the blustery weather, with famous faces like Super Ted and Big Bird from Sesame Street among them.
Winners Hehir, from Rathfarnham WSAF Athletics Club, and McCambridge, from Dundrum South Dublin (DSD), were both trained by former Dublin Marathon winner Dick Hooper.
The former emerged victorious after a long slog against Joe Sweeney who, in what was his race debut, came in second after 2 hours, 19 minutes and 26 seconds.
Sweeney, from DSD, was followed in third place in the men's category by Sergiu Ciobanu, from Clonliffe, with a time of 2 hours, 22 minutes and 2 seconds.
McCambridge became the first person - male or female - to win every race in the Airtricity Dublin Race Series. She previously won the five mile, 10 km, 10 mile, half marathon and now the Dublin Marathon.
Claire McCarthy, of Leevale Athletics Club, placed second in the women's category, with a time of 2 hours, 39 minutes and 37 seconds.
She was followed by Pauline Curley, of the Tullamore Harriers, who finished in 2 hours, 42 minutes and 58 seconds.
Paul Hannan emerged victorious in the wheelchair category, followed by Jim Corbett in second and Patrick Monahan in third place.
More than 10,000 Irish people took part in the marathon and a further 4,000 representing around 47 different nationalities travelled to the country.
Welsh National Champion Alun Evans was the only elite international male runner to participate.
Members of An Garda Siochana and the Police Service of Northern Ireland joined forces for the fifth year running and took part under the Garda Athletics Club vest.
The officers, who raised funds for different causes close to them, were cheered on by the Garda Band and the Assistant Commissioner for the Dublin Metropolitan Region.
Winners Hehir and McCambridge were awarded two years' free energy from marathon sponsor Airtricity and a brand new Renault Fluence ZE electric car.