Recent papers by Cathey and Demers (1975, 1976, 1977, ms) have incorporated an analysis of Old Icelandic phonology in which purely phonetically conditioned rules of i-Umlaut and u-Umlaut are crucial not only to the analysis itself, but to the theoretical implications theauthors draw from that analysis. Synchronically, however, the non exceptional application of i-Umlaut is restricted to just four morpho-syntactic classes: athematic and j-thematic verbs in the preterite subjunctive, j-thematic verbs in the non-preterite, adjectives with a consonant-initial comparative suffix, and athematic feminine or plural r-stem nouns. Historical u-Umlaut continues to round a to Q before u in the next syllable even in literary Old Icelandic, but its application is also morphologically induced, viz. a → Q in all feminines, plurals, and u-stems not followed by a vocalic suffix. All intraparadigmatic umlaut alternations are covered by these morphologizations, which in turn obviate the abstractions proposed by Cathey and Demers.