Groups were formed by draw, but did not have no more than one team from each provincial organization (the exception being Pichincha).
The teams played within their groups in a double round-robin tournament and in a local derby (Spanish: clásico).
The two teams with the fewest points in the First and Second Stage aggregate table were relegated to the Serie B for the next season.
In the Third Stage, the eight qualified teams were placed into two groups of four depending on their position on the aggregate table.
The national champion, runner-up, and third-place finisher will each have a berth in the 2010 Copa Libertadores.
Deportivo Azogues and Universidad Católica were relegated last season to the Serie B after accumulating the fewest points in the First and Second Stage aggregate table.
The winners of each group will advance to the Fourth Stage to contest the national title.
The group runners-up will also advance to the Fourth Stage to contest the third-place match.
The championship playoff will be contested between the winners of each Third Stage group for the national title.