This study investigated the relationship between vocabulary size and reading comprehension
performance among students in a tertiary institution in a Malaysian context and examined the
vocabulary size required for students to achieve reading comprehension at various levels of
proficiency. The research questions that guided this study were: 1) What is the vocabulary size of
second year diploma students studying Mass Communication?; 2) What is the reading
comprehension proficiency of second year diploma students studying Mass Communication?; and 3)
What vocabulary size is required for different levels of reading comprehension proficiency? This
study used the quantitative approach. The participants were 53 Malaysian second-year students at a
private university college in Malaysia who were reading for their Diploma in Mass Communication.
The instruments used were the Vocabulary Size Test and the IELTS Reading Test (Academic
Module). The findings showed that the average vocabulary size of the students was just over 6000
word families and this vocabulary size was generally insufficient for adequate reading
comprehension. Students needed an average vocabulary size of about 8000 word families to achieve
adequate reading comprehension and about 10000 word families to achieve proficient reading
comprehension. Based on the individual student’s performance, this study did not find a linear
relationship between vocabulary size and reading comprehension performance, nor was there a
threshold vocabulary size for adequate reading comprehension