Uefa president Michel Platini is to watch a trial match featuring four assistant referees in Slovenia today.
The new system is being deployed in a mini qualifying tournament for the Uefa European Under-19 Championship.
Two additional assistant referees will be placed behind the goalline to concentrate on incidents which occur in the penalty area.
The experiment with five match officials was approved at a meeting of the game's lawmakers, the International Football Association Board, in Scotland in March.
A separate proposal to experiment with goalline technology was discussed at the same meeting but put on hold.
The event in Slovenia makes up the group five qualifiers for the championship and features Norway, Slovakia and Armenia.
It begins today, when Platini will be in attendance, and runs until Wednesday.
Further trials are planned for groups one and seven, in Hungary and Cyprus, later this year.