28 teams, each plays the others once.
Additionally each team plays one more game in a round of traditional derbies (clásicos) - with hosting reversed compared to the first meeting between the two - for a total of 28 games each, over 28 game weeks.
3 points for a win, 1 point for a draw, 0 points for a loss.
1. points won; 2. special tie-breakers *; 3. total goal difference; 4. total goals scored; 5. points in head-to-head matches; 6. goal difference in hth matches; 7. goals scored in hth matches.
* - used only in case of a tie for 1st place.
1. points won; 2. play-off (only if exactly 2 teams are tied); 3. points in head-to-head matches; 4. goal difference in hth matches; 5. goals scored in hth matches; 6. total goal difference; 7. total goals scored; 8. draw.
Qualification for CONMEBOL competitions:
1-5 place: Copa Libertadores
Qualification for Copa Sudamericana
6-11 place: Copa Sudamericana
Relegation from the league:
Each team's points from participation in the 2015, 2016, 2016/2017 and 2017/2018 Primera División are summed, and that total is divided by the number of games played during that period (a total of 30, 46, 76 or 104 games).
Teams are ranked in a Promedio table, based on the resulting average score.
25-28 place in the Promedio table: relegated to Prim B Nacional
Promedio table order:
1. average points score; 2. play-off (only for deciding relegation).
Promotion to the league:
2 teams from Prim B Nacional