Arabic has a vowel system with three long and three short monophthongs. One of the parameters that accounts for qualitative differences between long and short vowels across languages is tenseness/laxness of vowels located on the peripheral/non-peripheral tracks in the vowel space. The present study investigates acoustical cues (F1, F2, and duration) of vowels using the data obtained from 21 speakers of Qatari Arabic. The vowels were produced in four phonetic contexts: labial, alveolar, uvular, and pharyngeal. The results revealed considerable qualitative differences between long and short vowels. The long vowels were articulated at the periphery of vowel space; the short vowels occupied more centralized positions. The co-articulatory effect of the preceding consonant was more prominent in short vowels. Short high vowels /i u/ were lowered toward the mid position; short low /a/ was fronted; long low /aː/ was retracted and raised. The findings suggest that short vowels in Qatari Arabic are lax and non-peripheral.