This study examines the use of cohesive devices and cohesive chains in the argumentative essays by Polish undergraduates majoring in English, using both quantitative and qualitative analysis. The analysis is based on the Halliday and Hasan (1976) framework on cohesion in texts. The book is divided into three chapters: two concerned with a discussion of the necessary theory of cohesion in texts and argumentative writing, and the third one is focused on the application of the theory- the analysis of essays. The analysis includes the distribution of cohesive ties and chains, some problems with using cohesive ties, and a comparative study of essays as regards the use of cohesive devices in two proficiency levels and in relation to writing quality. This study sheds some light on the concept of cohesion in written texts and how EFL students use cohesive features to express meanings in their writing.