At MIT, he was with Gabriele Veneziano, Emilio Del Giudice and Paolo Di Vecchia at the centre of an active school of theoretical physicists with close connections to Italy (with one of the Italian INFN and MIT financed "Bruno Rossi" exchange programs). He and his co-workers did fundamental work in string theory. Other well-known MIT colleagues at that time were Victor Weisskopf (who was recruited by Fubini to MIT), Steven Weinberg and Roman Jackiw. From 1994 to 2001, he was a professor in Turin. Fubini worked in the 1960s on current algebras and S-matrix theory (Regge trajectories among other things), in particular on their field-theoretical foundations. In the 1970s, he was with his MIT colleagues and pupils Gabriele Veneziano, Emilio Del Giudice and Paolo Di Vecchia one of the pioneers of string theory (the team introduced the so-called DDF states). He worked in the 1970s on other classical solutions of Yang–Mills equations and conformally invariant quantum field theory.