Kim, Hyung-Soo. 1999. Glide Formation and Compensatory Lengthening in Korean Revisited. Studies in Grammar 17, 15-31. This paper reanalyzes three phonological problems in glide formation and compensatory lengthening in Korean: 1) the obligatory glide formation with no compensatory lengthening in wa˘ <*o-a "come", 2) the lack of glide formation in coa <*coh-a "like, not ψcwa (cf. noa, nwa￣ "put"), and 3) the problematic use of global rules in explaining compensatory lengthening in examples such as na￣myen < *nah-imyen "give birth". These problems have been well known in previous analyses whose attempts to provide reasonable explanations have all failed. In this paper novel solutions to them are offered by making use of etymological reconstruction and preferential conditions on rules and the Principles governing their operation in Theoretical Phonology. In particular, the first problem is solved by reconstructing the underlying form of the verb o- "come" as *wΛ, whose stem vowel elides before vowel initial endings but undergoes contraction with the preceding w to become o: *wΛ-a >wa˘ but *wΛ-ta>ota. For the second and third problems, two new theoretical concepts are introduced to explain the rule ordering paradox and the use of global rules: 1) the principle of rule interruption that partially identical rules are interruptible and 2) the principle of strength conservation that morphological units such as words and syllables maintain a certain inherently constant strength.