The Blood Transfusion Service says over 100 people attended a dedicated clinic in Galway to try to find a suitable match for a local man in need of a bone marrow transplant.
Paul Giblin has been battling Hodgkin's Lymphoma since April 2012.
He has undergone radiotherapy and chemotherapy, as well as having a stem cell transplant.
He needs a bone marrow donor but an extensive trawl on a global registry has not yet yielded a match.
The 31-year-old is an accomplished athlete, with countless rowing medals at national and international level.
He has competed in cycling competitions in Ireland and abroad.
After qualifying as an engineer, he retrained and now works as an army officer, stationed at Dún Uí Mhaolaíosa in Galway.
His plight has generated extensive interest around the country, thanks to a social media campaign.
Friends of the army officer created the 'marrowmatch' hashtag to generate interest and they are appealing to people to give a sample to the global registry.
Lieutenant Giblin visited the clinic in Galway this afternoon and said he was heartened by the large turnout.
He pointed out that many lives could be saved, as a result of increased awareness about bone marrow transplants and the global registry.
Western Area Manager for the IBTS Carmel McNamara said hundreds of samples had been gathered from people across the country in recent weeks.
The samples - along with those given today in Galway - will be analysed to see if a suitable match exists.
If one is found, the donor's bone marrow is transplanted to Lt Giblin, in the hope it will help regenerate his marrow.
View the marrowmatch website here.
