This work aims to show the composition and performance of the Carlist parliamentary minority during the constituent Cortes from 1869 to 1871. The work of the so-called «white mountain» was the expression of the new Carlism project, determined to link its political cause with the defense of the Catholicism against the revolution as the most common and mobilizing element of the Spaniards of the time. Consequently, this minority joined every initiative to censor the Government and the Regency, presented amendments and proposals to support the Catholic unity and interests of the Church, and made propaganda speeches. In addition, he effectively carried out technical parliamentary obstructionism, in collaboration with the Republican minority, to prevent and slow down the legislative work of the majority.