The first bus carrying 11 evacuees, accompanied by Syrian Arab Red Crescent officials, arrived at a meeting point outside Homs as government soldiers stood by. The aid group expected around 200 people to leave.
Another person was brought out by ambulance from the Old City district, where activists said 2500 people have been under siege for more than a year, hungry and malnourished.
Russia said a three-day ceasefire had been agreed in Homs, which was one of the first cities to erupt in protest against President Bashar al Assad nearly three years ago and where street after street has been destroyed in fighting between the president's forces and anti-Assad rebels.
"It is foreseen that all children, women, men under age 55, as well as wounded people, can leave the combat zone without obstacle," Russia's Foreign Ministry said.
It said Syrian authorities had announced that evacuees would be provided with medical treatment and shelter. "Those residents of Old Homs who prefer to remain will be sent the necessary humanitarian aid," the ministry said.
Moscow, which has supported and armed Mr Assad throughout the civil war, hailed the Homs deal as a "landmark agreement".