Urban Qatari Arabic is a variety of Gulf Arabic [afb] spoken by Qataris with traditionally sedentary tribal backgrounds. This study examines phonetic and phonological aspects of Urban Qatari Arabic vowels using acoustic phonetic data gathered in Qatar. A new phonemic vowel inventory is proposed, including five long vowels and two short vowels. This finding contradicts published studies on Gulf Arabic, which include three or more short vowels; however, it is not unexpected when studies are compared from nearby Arabic varieties. The vowel inventory is also investigated using four linear mixed-effects regression models. In Gulf Arabic, variation in short vowel backness is largely accounted for by the point of articulation of adjacent consonants, as indicated by the statistical results. Word-final vowel raising is found to be conditioned by the preceding vowel in Urban Qatari Arabic. Typically, in other varieties of Arabic, word-final vowel raising is consonant-conditioned. A nuanced investigation of word stress, including interactions between stress and epenthesis, demonstrates significant microlinguistic variation. Epenthetic vowels generally can be stressed in Gulf Arabic, but for some speakers, stress assignment also depends on which type of epenthesis occurs. Diachronic variation in Gulf Arabic word stress is tending toward the elimination of stigmatized stress patterns and the introduction of stress patterns from non-Arabian dialects. Acoustic correlates of word stress are examined using the regression models. Pitch, duration and intensity are found to be statistically significant markers of stress. An examination of formants shows that contrasts in vowel quality are maximized in stressed vowels. A phonological analysis of epenthesis shows that it is generally predicted by sonority. Historical vowel deletion and synchronic epenthesis are demonstrated to be in a counterfeeding relation, which has previously led to conflicting claims about word final epenthesis. In three-consonant clusters, epenthesis is expected after the first consonant, but sometimes epenthesis occurs after the second consonant or does not take place. Although stress may be assigned to epenthetic vowels, epenthetic vowels differ phonetically from other short vowels. Furthermore, postlexical epenthesis differs phonetically from lexical epenthesis.