The man the US claims masterminded the 11 September attacks on New York and Washington is now being stalked from the air and on the ground, using the latest technology,.
Reports say the search is concentrating on the Tora Bora region near Jalalabad, east of Kabul.
Bin Laden is believed to be moving by night between caves in the honeycombed mountains, protected by a loyal band of Arab al-Qaeda fighters.
US Special Forces have been gathering as much information as possible from local people - or possibly captured Taleban fighters - on where Bin Laden could be hiding.
Their aim will be to find a precise location where the necessary firepower, from land or air, can be concentrated.
Interview
To encourage information, radio broadcasts and leaflets dropped from US planes are telling Afghans about America's offer of a $25m cash reward for Bin Laden's capture.
The last confirmed contact with Bin Laden put him somewhere north of Jalalabad, where he is thought to have a complex of training camps.
Journalist Hamid Mir, editor of the Dawn newspaper in Pakistan, was wrapped in a blanket and driven for five hours from Kabul before interviewing Bin Laden in early November.
That suggests he was only 75km (47 miles) from the capital.
He recalled colder temperatures and the sound of anti-aircraft fire which could mean he was driven north.
But Mr Mir said that, by holding the interview in the north, Bin Laden may have trying to draw attention away from his bases elsewhere in the country.
Another clue was the rock formations seen in a video released by Bin Laden which a geologist traced to the region of Khost in Paktia province.
Deep underground bunkers in the area, built during the war against the Soviet Union, are large enough to hide tanks.
Escape routes
In 1998, the Taleban showed the BBC what they said was a camp in Khost run by Bin Laden. It had been attacked by US cruise missiles in retaliation for bomb attacks on embassies in Kenya and Tanzania.
Some Northern Alliance sources believe Bin Laden is in a place called Maruf, 120km (75 miles) east of Kandahar.
However, Haji Gul Agha, a Pashtun anti-Taleban leader and former governor of Kandahar, said that if Bin Laden was in the province it would be in the south-west.
US Marines are now based near Kandahar controlling an airfield and cutting off possible escape routes for al-Qaeda fighters.
They have the latest technology at their fingertips in their search for Osama Bin Laden.
Beacon
The New York Times, quoting unnamed government officials and scientists, reports that an array of sensors can penetrate 100ft of rock to detect the heat from bodies, the hum of a generator or magnetic signals from electrical wiring.
The devices can be carried by aircraft or soldiers, or towed behind vehicles.
Scientists who helped develop the equipment say that the slightest waft of warm air from a tunnel or cave will stand out like a beacon from miles away.
The worsening winter in Afghanistan will make those beacons even brighter, possibly helping to deliver Bin Laden into the allies' hands.