The besieged Damascus suburb of Darayya has received its first aid convoy since November 2012, according to the Red Cross.
UN aid officials had said the town was suffering dire shortages of food, clean water and medicine.
A 48-hour ceasefire for the town, which lies south of the Syrian capital, came into force early on Wednesday.
Vaccines, baby milk, medicine and nutritional goods were being delivered, the UN's humanitarian arm said.
Separately, the rebel-held town of Muadhamiya, north-west of Darayya, received deliveries of food parcels and wheat flour on Wednesday, a month since aid convoys last visited.
In April, the UN said at least 4,000 people were besieged in Darayya by Syrian government forces.
Its electricity supply was cut off more than three years ago.
Speaking in April, UN emergency relief co-ordinator Stephen O'Brien said the Syrian government had ignored "countless" requests for aid to be allowed in.
An aid convoy was blocked from entering the town last month, despite all involved parties agreeing aid could be delivered.
The latest delivery was made by teams from the UN, the International Committee of the Red Cross and the Syrian Red Crescent.
Russia's defence ministry said on Wednesday it had agreed a pause with the Syrian authorities for 48 hours to allow for the distribution of humanitarian aid in Darayya.
It borders a military airport used by Russian planes in support of the government of President Bashar al-Assad.
It was one of the first towns to report demonstrations against the Assad regime, and has been under siege since late 2012. The UK-based Syrian Observatory for Human Rights reported clashes this week between rebel groups and government fighters on the outskirts of Darayya.
The UN believes there are more than 4.6m people living in hard-to-reach areas in Syria, including nearly 600,000 in besieged areas.