The current paper explores the silent behavior of students within EFL classrooms. It investigates reasons behind students' in-class silence, or lack of verbal participation, and then puts forwards several suggested solutions for more effective in-class conversation. The population for this study consists of 85 English-major students at a university of foreign languages in Hanoi, Vietnam and the data are collected via questionnaire and semi-structured interview. The findings indicate various causes of students' classroom silence: personal and impersonal, linguistic and psychological factors such as students' personality and language proficiency, teachers' methodology, lesson contents, and class cooperation. Together with the theoretical discussion, the empirical evidence revealed by this study can perhaps help applied linguistics practitioners/ teachers gain more heightened awareness and deeper understanding of students' silent behavior. The current study purposefully targets at enhancing both the English teaching and learning efficiency at this foreign-language university.