This study was designed to investigate the washback effects of Secondary Certificate English exam on both teachers and students' practices in Oman. It also aimed to determine the extent to which these practices may vary according to certain variables, such as students' and teachers' sex, teachers' experience and students' stream. To attain the purpose of this study, four general questions and ten sub questions were developed. The general questions were stated as follows: 1. What are the washback effects of the Secondary Certificate English Examination on the teaching process? 2. What are the washback effects of the Secondary Certificate English Examination on the learning process? 3. Is there a statistically significant difference in the washback effects of Secondary Certificate English Examination on the teaching process that can be attributed to sex and / or to teaching experience? 4. Is there a statistically significant difference in the washback effects of Secondary Certificate English Examination on the learning process that can be attributed to sex and / or to the stream? The sample of the study consisted of 54 third secondary teachers and 157 students in the Muscat area in Oman. In order to deal with the research questions, two self-report questionnaires were developed, one for the teachers and another for the students. The items in the questionnaires revolved around five dimensions, these mmar and vocabulary, language skills, areas of exam changes, time management and the match or mismatch between the ELT textbook and the exam. The findings indicated that there was a washback effect for both the teachers and the students in all the five dimensions. They also showed that there were no statistically significant differences between less experienced and more experienced teachers and between male and female students in the washback effect. However, there were statistically significant differences between male and female teachers in the dimension of grammar and vocabulary and the dimension of time management. Male teachers were more influenced by the exam than the female teachers. Statistical differences were also found between arts and science students in the dimension of grammar and vocabulary and in the dimension of exam changes. The art students were more influenced by the exam than the science students. The study concluded with some recommendations for third secondary teachers and for material developers.