Following upon an article of J. Healey, this study emphasizes the continuity between the Edessean script of every day life, attested in Middle Euphrate parchments of the 3rd century as well as partly on mosaics, and the serto script attested in manuscripts from the 8th century onwards. Some intermediate examples can be found in colophons of 6th century manuscripts. This shows that the serto script originated in the region where the Edessean script was in common use, in Upper Mesopotamia and along the Middle Euphrates, whereas in Mesopotamia, the common script was of oriental aramaic style and the Edessean script was only known under its estrangela form. The serto script was originally a regional script and only became secondarily a confessional one