This is a detailed study on the insertion of epenthetic vowels in verbal and nominal forms primae and mediae gutturalis, in Biblical Hebrew, as well as in normative and spoken Modern Hebrew. The monograph aims at showing the following: 1) Apparent irregularity in a linguistic system, here on the phonological level, can be resolved within a network of transparent rules, which reflect the interaction of various parameters. 2) The tension between the norm and the corresponding reality in a linguistic system is by no means just a modern phenomenon, but can, in the case of Hebrew, be traced all the way back to the classical stages of said linguistic system. 3) The sonority scale in conjunction with the relevant preference laws for syllable structure has once again proven to be a powerful explanatory device in phonological theory and emerged as the central argument in the context of our research. 4) Optimality Theory offers a theoretical framework for arranging an array of relevant constraints in order to account for the variety of observable output forms in the Tiberian Hebrew tradition, many forms of which continue to be valid in modern times.