Videophone links were introduced earlier this year
Some of the detainees held in US custody at the Bagram air base outside Kabul, Afghanistan, are being visited by their families for the first time.
The Red Cross said five families were being allowed to visit Bagram for hour-long visits with relatives.
The visits were arranged after the Red Cross brokered a deal with US military authorities to allow family visits.
The organisation has always maintained that family visits to detainees are allowed under international law.
The US military considers the men "unlawful combatants" who can be detained for as long as they are deemed a threat to Afghan national security.
Earlier this year the International Committee of the Red Cross (ICRC) introduced video calls for relatives to make contact with those held inside Bagram.
But Tuesday's visits, for an initial group of 20 people, took access a step further.
"The first time I saw Safiullah on the screen, I just cried. I was so happy and sad at the same time. But this time it will be different," said Mohammada Jan, whose brother-in-law is being held at Bagram.
"When we visit him in Bagram, we want to make sure that he is not upset about seeing us, but draws strength from the experience," she told the Red Cross.
US commanders agreed to allow the visits after years of negotiations by the Red Cross, although it remains unclear whether there will be a physical barrier between the detainees and their families.
The Red Cross has had regular access to prisoners at Bagram since 2002, and recently set up a video link system to allow families the chance to talk to relatives detained there.
"The videophone system was an important first step in reassuring family members that their relatives held in Bagram were alive and well, and vice versa," said Franz Rauchenstein, head of the Red Cross delegation in Afghanistan.
"It gave them the opportunity to see and speak to one another."
"We have continued to work with the US authorities to make such visits a reality, and we are very happy for the families that they now have this opportunity."
In the past there have been reports of detainees at Bagram facing harsh interrogations. In 2002, two Afghan detainees died after being repeatedly struck by American personnel.
Families of many of the detained men say that initially they had no idea where their relatives were being held, and then had only sporadic communication by letters delivered by the Red Cross.
The US already allows visits to family members at some detention centres in Iraq.