This study aims at identifying some of the factors that have a bearing on the reading achievement of ESP students. The research questions were: (1) What are the factors which underlie the students’ reading performance? and (2) What test tasks influence their reading achievement? The findings of the first question indicate that there are three factors which underlie adequate understanding of texts: (i) lexical knowledge, (ii) coherency, and (iii) comprehension. The findings of the second question indicate that the students performed moderately on the „local‟ reading skills as well as on „global‟ reading skills and strategies.