Despite the importance of research article abstracts and difficulties that English L2 writers encounter when writing research articles in English in the field of medicine, little research has investigated lexical bundles in medical journal abstracts. This paper explores the structural and functional characteristics of lexical bundles between two corpora consisting of medical journal abstracts written by English L1 and L2 writers, respectively. The findings, from extensive use of verb phrase-based (VP-based) and text-oriented bundles by English L2 writers, as well as that of noun phrase-based (NPbased) and research-oriented bundles by English L1 writers, show that English L2 writers lack awareness of discipline-specific bundles in medical journal abstracts. The findings of the study would be a valuable source for English L2 writers to explore the use of lexical bundles by English L1 writers in medical journal abstracts reporting clinical trials and randomized controlled trials, thereby helping them develop a better understanding of medical journal abstract conventions.