While much is known about Latin orthography little is known about Arabic orthography. This study investigates the effect of vowels on reading accuracy in Arabic orthography. Participants were 64 native Arabic speakers. Four kinds of written Arabic texts were administered: narrative, informative, poetic and Koranic. Three texts of each kind were presented in three reading conditions: correctly vowelized, unvowelized and wrongly vowelized. Results indicated that vowels had a significant effect on reading accuracy of poor and skilled readers in reading each of the four kinds of texts. The results are discussed in light of the concept that more cross-cultural considerations should be made in reading theory today.