This study is concerned with the identification and the analysis of errors in tense (ET) in the written English of Turkish students and the implications of such errors in foreign language teaching. Because of limitations which will be explained below, only three tenses were taken into consideration in the analysis. These three tenses were: a) the simple past, b) the past perfect and c) the present perfect. A data collection technique was selected which involved the collection of writing samples on a topic designed to elicit the verb tenses under consideration. The data analysis was designed to yield quantitative generalizations on the relative frequency of ETs in the writing of Turkish students at different levels of advancement in English.