the present study were to identify the different types of pronunciation errors in the consonant and vowel sounds made by Omani grade ten students, to compare the frequency of these errors made by males and females, and to explore the perceptions of the English teachers and supervisors regarding the causes of such errors. The population of this study consisted of all grade ten male and female students in cycle two schools in South Batinah. The total sample of students was 25 males and 27 females. It also included 50 teachers and 19 supervisors. To answer the research questions, the researcher used two main instruments: 1. Word lists which included the consonant and vowel sounds in words. The words were chosen from the books of grades 1-9. 2. A questionnaire to identify the causes of these errors as perceived by teachers and supervisors. The major findings of this study are: 1. The students had problems with the following consonant sounds; a. Initial/p/, Medial /p/ and Final /p/ in plosives. . b. Medial /1, Medial /3), Initial /v/, Final /v/, Initial /0/, Final /0/ and Final /// in fricatives. c. Medial /y/ and Final /n/ in nasals. d. Initial /ts/, Medial /ts/, Final /ts/, Initial /d3/, Medial /d3/ and Final /d3/ in affricateş. e. Medial /j/ in approximates. 2. The students faced serious problems with the following vowel sounds: a. The long vowels /i:/ and /u:/.. b. The short vowels // and /n. c. The diphthongs /e1/, /41/, /40/, ləv/, /13/, leal and /vəl. 3. There was no significant difference between grade ten male and female students in the errors of all the consonant sounds. However, there were significant differences between males and females in the short vowel (11/), and the diphthongs (lau/) and (lue/),which were mispronounced by more males than females, and the diphthong (/18/),which was mispronounced by more females than males. 4. The most frequent causes of pronunciation errors, as perceived by the teachers and supervisors were: • The irregularity of English spelling in relation to pronunciation; • Students not listening to native speakers to acquire their pronunciation of the English sounds; The differences in the sound systems of English and Arabic; • Learners' negative attitudes towards the learning of a foreign language; and • Lack of motivation and interest in learning the correct pronunciation. 5. There was no significant difference between teachers and supervisors in their overall perceptions of the causes of errors in producing English sounds.