The team achieved its first win in its first game in its first season in the 1st division by 89–67 against Breogán. This season, the Basque team became strong at home by winning direct rivals avoiding the relegation six rounds before to finish the league by winning in Bilbao and debuted in the Copa del Rey reaching the semifinals where were eliminated by Estudiantes. In the 1973–74 season, the club reached 1,400 supporters and this support allowed to sign its first foreign player, the Canadian Phil Tollestrup. This second season, the team concluded the league in eighth position and it gain the right to play in Korać Cup, but it had to resign due to lack of budget.