In 1942, aged 19, he entered the PSI and took part in the Italian resistance movement, as a member of the partisan bands operating in the Colli Albani.

In 1958, after the death of his father, he was elected to the Chamber of Deputies for the Italian Democratic Socialist Party (Partito Socialista Democratico Italiano; PSDI), where he remained until the end of the XI legislature in 1994.

He was subsequently the Minister of Scientific Research on three occasions, in the Andreotti II (1972–1973), Forlani (1980–1981) and Fanfani V (1982–1983) Cabinets.

In early 1989 he left the party and, together with Pietro Longo, founded the Movement of Unity and Socialist Democracy (Movimento di Unità e Democrazia Socialista; UDS), which merged later that same year with the PSI.

After the disbandment of the PSI in 1994, he entered the newly formed Italian Socialists (SI) and then, from 1997, the Democratic Party of the Left (PDS).