The present investigation is descriptive-interpretative in nature. It has been designed a) to describe types of language learning strategies which Thai engineering students reported employing; b) to investigate patterns of variations in frequency of students' reported strategy use with reference to type of institution, gender, `perceived' class size, location of institution, and language proficiency levels; and c) to examine the relationships between frequency of students' reported strategy use and the five independent variables. Two main strategy categories, i. e. classroom-related, and classroom-independent, have been examined. The data for the investigation were collected in two phases with different instruments. Semi-structured interviews, and a strategy questionnaire were used as the main methods for the first and second phases of data collection respectively. The thesis comprises eight chapters. Chapter one is an introduction to the thesis. It provides both a background and a context to the present investigation. Chapter two presents the review of related literature and materials on language learning strategies in order to locate the present investigation in the context of previous research and authors' opinions. Chapter three reviews research methodology in language learning strategies, and the conceptual framework for the present investigation. Chapter four presents how the strategy inventory for the present investigation has been generated as the results of student interviews, and the construction of the strategy questionnaire. Chapter five presents the processes of the construction and validation of the proficiency test which was used to determine students' language proficiency levels. Chapter six examines frequency of strategy use reported by 570 Thai engineering students, ranging from overall strategy use to use of strategies at the individual level. Statistical methods such as mean of frequency, standard deviation, and percentage are used to help interpret the data. Chapter seven examines the relationships between frequency of students' reported use of strategies and the five variables. In doing so, an analysis of variance (ANOVA), chi-square tests, and a factor analysis are used as the main statistical methods. Chapter eight summarises the findings of the investigation and discusses the results of the research findings. In addition, the Chapter discusses limitations of the present investigation and proposals for future research. as well as the implications for the teaching and learning of English for engineering students in Thailand. The findings of the research show that Thai engineering students, on the whole, reported medium frequency of strategy use. They reported higher frequency of use of classroom-relateds trategies than classroom-independenst trategies. The results of the data analysis also demonstrate that frequency of students' overall reported use of strategies varied significantly in terms of `type of institution', and `language proficiency levels'. Regarding `gender', `perceived' class size, and `location of institution', these three variables were not found to have much relationship to students' choices of strategy use. The results of the investigation also suggest that language proficiency may be related to students' employment of out-of-class strategies, especially those involving utilising media, as well as computer programmes in English as a source of the target language input.