La costanza della ragione is a 1964 drama film directed by Pasquale Festa Campanile,[1] based on the homonymous novel by Vasco Pratolini and starring Sami Frey and Catherine Deneuve.

[2][3] Bruno, a young idealist, would like to be hired in a large company.

[4] Produced by Pasquale Festa Campanile and Massimo Franciosa for Franca Film (Rome), in co-production with S.N.D.C.

of Paris, the film was shot in the summer of 1964 for the exteriors in Tuscany and for the interiors in the Studies of the SAFA Palatino, to go out in theaters in the first screening on 27 November 1964.

First Italian film for Catherine Deneuve and Samy Frey.