Spelling is a basic literacy skill in any language as it is crucial in communication. EFL students are often unable to spell or pronounce very simple monosyllabic words even after several years of English instruction. Similarly, teachers and researchers usually focus on the larger skills such as speaking and reading and ignore the smaller components. This study attempted to investigate the problems that university Arab learners face in spelling English vowels. The reason for focusing on vowels is that they appear to be more problematic and irregular than consonants, probably because of the perceptible mismatch between phonemes and graphemes. The study has primarily focused on monosyllabic words in order to (a) test the students' knowledge in spelling these basic words and (b) to avoid the impact of other factors, such as stress and intonation which affect the pronunciation of vowel sounds in multi-syllable words. Data were collected through a battery of tests. The study has important implications for future research and for teaching.