ABSTRACTThe objectives of the study are to find out whether or not (1) there is acorrelation between vocabulary mastery and reading ability (2) there is acorrelation between grammatical competence and reading ability and (3) there is acorrelation between vocabulary mastery and grammatical competencesimultaneously and reading ability.The correlation method is used in this research that was carried out atEnglish Department of Teacher Training and Education Faculty, Sebelas MaretUniversity in September 2014 with total of the population is 70 students. Thesample of this research is 30 students from Class B which was taken randomlyusing simple random sampling. The data of vocabulary mastery, grammaticalcompetence, and reading ability in this research were collected using test. Thedata are then being analyzed using simple correlation and multiple linearregressions.The research findings show that (1) there is there is significant positivecorrelation between the students’ vocabulary mastery and reading ability with thecoefficient of correlation (rx1y) 0.5469 and the significance of coefficient ofcorrelation (to) 3.4571 which is higher than t table at the level of significance a =0.95 for n = 30 is 1.70 (2) there is significant positive correlation between thestudents’ grammatical competence and reading ability with the coefficient ofcorrelation (rx2y) 0.5377 and the significance of coefficient of correlation (to)3.3753 which is higher than t table at the level of significance a = 0.95 for n = 30is 1.70 and (3) there is positive significant correlation between the students’vocabulary mastery (X1) and grammatical competence (X2) simultaneously andreading ability (Y) with Fo (8.22) which is higher than Ft at the level ofsignificance a = 0.05 and the df (degree of freedom) for n = 30 is 3.35.From the results of the study, it is known that (1) the first hypothesisstating that there is a positive and significant correlation between vocabularymastery and reading ability is accepted (2) the second hypothesis stating that thereis a positive and significant correlation between grammatical competence adreading ability is accepted and (3) the third hypothesis stating that there is apositive and significant correlation between vocabulary mastery and grammaticalcompetence simultaneously and reading ability is also accepted. It can beconcluded that reading ability will simultaneously follow the increase anddecrease of vocabulary mastery and grammatical competence.Key words: correlation study, vocabulary mastery, grammatical competence,reading ability