This paper has attempted to make a preliminary srudy of lexical errors of adult learners of English with a view to finding out the following: i) the type of lexical errors learners make ii) how these errors can be explained iii) to what extent these errors affect effective communication with regard to the first aim different types of errors such as errors of retrival, speech perception, sense relations, LI influence etc, were found in the data. with regard to the second aim it was found that most of these lexical errors were due to learners' incomplete knowledge of a word and some were due to LI transfer, mainly as a result of using bilingual dictionries. It was found that though most of these errors did not affect comunication, they need to be corrected before they become fossilised.
