This contribution deals with the history of the attempts to introduce the so-called “Modern Mathematics” into teaching, since the 1960s. After a short presentation of the global situation, we focus on the case of Italy. We will present the development of the phenomenon and focus on the opinion of teachers and mathematicians who were involved in the debate. We mention some of them and we focus on why Modern Mathematics in Italy, even if it had a limited diffusion, influenced the entire debate on mathematics teaching that took place after the 1960s.