This paper investigates all aspects of the orthography of the Ormulum in relation to the phonology of the late twelfth-century south Lincolnshire dialect which Orm's spelling system was designed to reflect. We show that Orm's adaptations of what he found in existing orthographic systems provided a set of graphic symbols that was fully capable of representing phonological contrasts in the vocabulary of the dialect and which thus in many respects resembled the inventory that an analysis on phonemic principles might provide. However, Orm's system has more orthographic symbols than an analysis of distinctive oppositions in speech would have required. All of these additions are in some measure attributable to following precedent. In this aspect of his spelling system, as in his innovations, nearly all of which also have parallels within the English orthographic tradition, we discern a spelling reformer who, in due consideration of transparency of the system as perceived by the reader, took pains to depart as little as possible from the familiar.