Abstract. The dominant characteristics of spoken vowels are the two first formants. Thus the vowel systems of many different languages have been documented and compared through their F1-F2 space. Hebrew and Spoken Arabic, both Semitic languages, have five basic vowels: /i e a o u/, though Spoken Arabic has both short and long versions of each. In this paper we present an overview of the results of several studies on vowel formants in both languages. We first compare formants of isolated phonation and connected speech in Hebrew, showing how the formant space is reduced drastically in connected speech as compared to isolated phonation, and how in some cases a clear assimilation to surrounding context can be observed. We then present results on read speech in two Arabic dialects. We show the subtle differences between the two, and discuss the effect of vowel duration also. Finally we discuss how the results can be influenced by the research methodology, and comment on the relevance of the results to speech processing technologies.