The crucial role of vocabulary knowledge in reading comprehension has been well recognized in first language (L1) situations and this has appeared to be true of second language (L2) settings as well. However, in relation to a sociocultural context such as Singapore, where English is designated as an L1 in the school curriculum but the majority of students still learn it as an L2, little is known about how students' vocabulary size could affect their reading comprehension. Given that students and teachers often cite vocabulary as the biggest hurdle in reading, this study was undertaken to explore the role of vocabulary in reading comprehension. Thirty-seven year-4 secondary students in a neighbourhood school in Singapore participated in this study. The Vocabulary Levels Tests were used to measure students' vocabulary knowledge in relation to the different measures intended to test their reading comprehension and summary abilities. Results suggest that students' vocabulary knowledge at the 2,000-word and the 3,000-word levels was correlated to their reading comprehension. Significant correlation yielded only for the short-answer questions, but not for the summary. Pedagogical implications and recommendations for further research are also discussed. (Contains 2 tables and 1 note.)