There was an estimated 120,000 people at the 1916 commemorative parade in Dublin today.
In a formal ceremony outside the GPO at noon, the President and the Taoiseach listened to a reading of the Proclamation and observe a minute's silence.
Ms McAleese laid a wreath in honour of those who died in 1916.
The President then took the salute as 2,500 members of all branches of the defence forces paraded in the capital.
It included the reserve force, and members of both the Organisation of National Ex-servicemen and the UN veterans' association.
The parade also included representatives of An Garda Siochána, to honour their service with the UN.
The Taoiseach earlier laid a wreath in Kilmainham Jail to the men executed after the 1916 Easter Rising.
Among those present in the Stonebreakers' Yard, otherwise called the Execution Plot, was Fr Joseph Mallin, son of Michael Mallin who headed the Irish Citizen Army at the Rising.
Mr Ahern said today's ceremonies were 'about discharging one generation's debt of honour to another'.
He praised the 'pariotism and vision' of the men who, he said, 'set in train an unstoppable process which led to this country's political independence.'
We now aspire, Mr Ahern said, to a future where the next generation of Irish men and women can confidently build on these foundations of prosperity and peace and also make their own contribution both at home and in the wider world.
And he pledged to continue to work for peace, for justice, for prosperity and for reconciliation between all who share and who love this special island.