Correlation between the mastery of vocabularies and reading comprehension achievement

English is one of the most important languages to be learned because mastering English might help a person increase his knowledge such as education, technology, culture, and other sciences. One of the ways to achieve the knowledge is by reading much. Nowadays reading becomes an important skill in education processes. The advantages of reading are to gain information and for the future career who wants to keep abreast of the latest development in the world. The main emphasis of the teaching of English as a Foreign Language in Indonesia is on the students' ability to read in English. Reading foreign books are more difficult than reading Indonesian books, because the students often find unfamiliar words in the English books. This problem can be solved by consulting the dictionary or by guessing the meaning through context. It is really important to master the vocabulary because without mastering enough vocabulary the students will not be able to understand the reading passage. A good reader should master vocabulary, and is able to predict its meaning by making use of his knowledge of the words and contextual clues available in the printed texts. This study is carried out mainly to find out whether there is a relationship or correlation between the mastery of vocabularies and the reading comprehension achievement. The subject of this study is the second year students of SMU Stella Maris Surabaya in the academic year 1996/1997. The data obtained from two kinds of tests (the vocabulary test and the reading comprehension test) are correlated using the formula of Pearson Product Moment Coefficient Correlation. The result of this study indicates 689 coefficient correlation. It proves that there is a linear positive correlation between the mastery of vocabularies and reading comprehension achievement. In other words, if the students' mastery of vocabularies is high, their reading comprehension achievement is also high. The coefficient determination percentage of the influence of mastery vocabulary toward the reading comprehension achievement is 47,47%. It means 47.47% indicates influence of the mastery of vocabularies, while 52.53% indicates the influence of some other factors toward the reading comprehension. Looking at the result above, it is suggested that the senior high school students should be given a lot of practices on vocabularies through reading passages. The students' knowledge of vocabularies can help them understand the reading passage they are reading. Furthermore, it would be better if there is a cooperation between vocabulary and reading in presenting the material