The aim of this paper is to explore the phonetic nature of vowels in Modern Standard Arabic (MSA). Although Arabic is a Semitic language, the speech sound system of Arabic is very comprehensive. Data used for this study were elicited from the standard speech of nine informants who are native speakers of Arabic. The researchers used themselves as informants, they also benefited from three other Jordanians and four educated Yemenis. Considering the alphabets as the written symbols used for transcribing the phones of actual pronunciation, it was found that the pronunciation of many Arabic sounds has gradually diverged from the standard. The study also discussed several related issues including: The phonetic description of Arabic vowels, classification of Arabic vowels, types of Arabic vowels and distribution of Arabic vowels.