This study analyses "Al-?i?laal" phenomenon which takes place in Modern Standard Arabic (henceforth, MSA) derivational processes. Based on the description of Arab traditionalists such as Al-Raagihi (1984: 155) and AlGalaayiini (1991), "Al-?i?laal" is defined as "a change that occurs with vowel letters where they can be deleted or substituted by another letter in certain cases". For example, the letter "w" in "da?aw" "prayed to God" is substituted by the letter "a" in "da?aa" (Al-Raagihi 1984). Clearly, the previous example analysed by Arab traditionalists demonstrates that the changes that take place are heavily reliant on the orthography of MSA, rather than the phonological system. For instance, /y/ and /w/ are regarded as vowels, rather than glides or semi vowels. Therefore, this study analyses examples of words in which "Al-?i?laal" takes place based on autosegmental or non-linear phonology; an approach in which phonological representations consist of several levels or tiers (Goldsmith 1979). The analysis of the words reveals that there is actually no substitution of sounds and the change that occurs in these words is phonologically motivated. Finally, the study recommends the reconsideration of the concept of "Al-?i?laal" in Arabic morphological literature to account for the phonological changes that occur in these words.