The potentially preventative medicines were taken under strict security to a secret location in the West African country.
Scientists aim to immunise 30,000 volunteers, including front-line health workers.
More than 8,500 people have died in the Ebola outbreak, the vast majority in Guinea, Liberia and Sierra Leone.
The total number of reported cases is more than 22,000. In Liberia alone, more than 3,600 people have died from the disease.
But the number of Ebola cases in Liberia has been steadily
decreasing, with only four confirmed cases in the week leading up to 25
January.
According to the World Health Organization (WHO), the
epidemic has entered a "second phase" with the focus shifting to ending
the epidemic.
The trial beginning on Monday involves
injecting a small amount of a strain of the Ebola virus into 12
volunteers in order to trick the body into producing an immune response.
More volunteers will be immunised as the trial progresses.
However, it is not yet clear whether the trial vaccines will offer protection against the disease.
