The main purpose of this paper is to investigate the myths, which were the main source of inspiration for the tragic poets of the 4th century b.c. To begin with, the fact that several tragic poets of the post-classi-cal period invent or introduce —to some extent— interesting innovations in the composition of well-known myths will be discussed. In other words, the tragic poets seem to introduce new variations of the traditional myths, whichemphasize more the passive or melodramatic element. Tragedy seems to have been still a vibrant literary genre in the 4th century b.c. Theatrical production was not limited, but rather expanded beyond Athens. Then, it will be arguedthat the action of the heroes of the mythical house of Kadmos was the dominant source of inspiration for the dramatists of the 4th century b.c. The other major mythological cycles were probably exploited on a limited scale by thetragic poets. Finally, an attempt will be made to answer the question why the tragic poets of the 4th century b.c., most of whom were Athenians, insisted on deriving themes from the mythological tradition of Thebes.