1950 when the Guayas Football Association () turned professional and held its first professional tournament for affiliated clubs (for clubs in Guayaquil). The Professional Football Championship of Guayaquil () was first held in 1951 and was won by Río Guayas. In 1954, the football association in Pichincha (current the Asociación de Fútbol No Amatur de Pichincha [AFNA]) decided to turn professional and hold a professional tournament of their own for their affiliated clubs (for clubs in Quito & Ambato). The first Inter-Andean Professional Championship () was held in 1954 and was won by LDU Quito. The two tournaments were the top-level football leagues in Ecuador, but the champion of each could not claim to be the national champion. That changed in 1957 when a national football tournament was organized for the winners the two leagues. The first Ecuadorian Football Championship was contested between the champion and runner-up of the 1957 Campeonato Professional de Fútbol de Guayaquil of (Emelec & Barcelona, respectively) and the champion and runner-up of the 1957 Campeonato Professional Interandino (Deportivo Quito and Aucas, respectively). Emelec won the tournament and became the first national champions of football in Ecuador. No championship was held in 1958 and 1959. The tournament returned in 1960 using the same format as in 1957. This time the field grew from four teams to eight teams. This format continued until 1967 when a number of changes occurred: 1) the regional tournaments were discontinued after the 1967 season; 2) teams contesting the national championship from 1968 onwards were now part of the Primera Categoría; and 3) a second level of Ecuadorian football (Segunda Categoría) was put into play and a system of relegation and promotion began in 1967. In 1971, the Primera Categoría was divided into two Series: Serie A & Serie B. Serie A was to be the top level of club football, while Serie B was the second, and Segunda the third. Between, 1983–1988, Serie B was merged into the Segunda, but the Serie A continued. Serie B was brought back in 1989, and has stayed as the second level since. In 2005, the Campeonato Ecuatoriano was divided into two tournaments to crown two champions in one year. The two tournaments were called Apertura and Clausura. The tournament returned to its year-long format in 2006. Clubs A total of 55 clubs have competed in the Serie A since the first season in 1957.