The Health Service Executive has said 2,650 people had registered for the free GP care for the over 70 services by 4pm today.
More than 35,000 people, who are not currently entitled to free GP care, will be covered under the scheme, which begins next Wednesday.
It is the next step towards the Government's plans for universal healthcare - an end to two-tier public-private medicine.
Following the roll-out of free GP care for all under-sixes last month, all those aged 70 and over will now have free access to their GP.
Speaking on RTÉ’s Today with Keelin Shanley, John Hennessy, HSE National Director of Primary Care, said that somewhere between 35,000 and 40,000 pensioners will benefit from the extension of free GP care.
Mr Hennessy said registration was already up and running: "We already have over 550 registered by 10am this morning. If you contact our website gpvisitcard.ie, you can register very simply online.
"If you wish to apply in a more traditional manner,using an application form, those forms are very available at the health centres, GPs and pharmacies.
"And anybody by the way can get help and advice by contacting our helpline at 1890 252 919," he added.
Mr Hennessy also said an eligible person could also apply through a nominated contact for example, a son or a daughter.
Earlier, Minister for Health Leo Varadkar said it is an important second step on the way to universal health care.
Speaking on RTÉ's Morning Ireland, Mr Varadkar said for the first time, the eldest and youngest in society will be able to access GP care without being charged.
He said the scheme is likely to cost about €18-€20m in a full year.
He added: "But it is good news, essentially it kicks in on 5 August but people can start registering from today.
"If you already have a medical card or a GP visit card and you're 70 or older, you don't have to do anything," Mr Varadkar added.
Dr Tadhg Crowley, from the Irish Medical Organisation's GP committee, welcomed the move but said he was disappointed that the 35,000 people eligible for the GP visit card will not have access to Allied Health Professionals such as public health nurses and physiotherapists under the scheme.
He also said he would like Minister Varadkar to address problems regarding preventative healthcare in the current GP contract from the 1970s.