Liga was the highest level of amateur football, although a number of teams had professional or semi-professional players in their ranks.
Within each group, the teams would play a double round-robin to decide their positions in the league.
The three groups winners and three runners-up, together with the two best third placed teams, then contested a play-off for the two promotion slots.
Group 2 champions were Basel U-21, but they were not eligible to the play-offs, this right was passed down to second and third placed Biel-Bienne and FC Solothurn.
They were also joined by FC Baulmes and SC YF Juventus who had just suffered relegation after the 2003–04 Challenge League.