Following the general elections on 29 October 1989, Ruiz-Gallardón continued serving as a senator for Madrid and, as in the previous legislature, headed the PP Parliamentary Group in the Senate. He returned to the PP's National Executive Committee at the Tenth Congress, this time with José María Aznar as party chairman. He also retained his position as president of the Committee on Conflicts. In April 1990, he headed an internal investigation of the "Caso Naseiro". This investigation resulted in the expulsion of several party officials.