English titles of medical research articles (RAs) are of great importance, the quality of which can, to a certain degree, affect impact factors of the articles, because many readers will make a decision as to whether to read on after reading titles. However, the special genre has not been extensively studied to date. This paper is designed to reveal the syntactic structures used in English titles of medical RAs to meet one of the qualities of effective titles, conciseness or economy. A total of 417 titles from original articles published between July 2003 and July 2005 in the "New England Journal of Medicine" were thoroughly analyzed structurally. Nominal groups rather than other structures were widely used in the corpus, with a surprising frequency (99%) while the remaining titles (only 4) began with a gerund. Three types of nominal groups, including "uni-head", "bi-head" and "multi-head" nominal groups, and their subtypes were identified. Then, all the nominal groups were functionally analyzed in terms of both post-modifiers, including Prepositional Group, To-infinitive Clause, Past Participle and Present Participle, pre-modifiers. The study may be helpful for those concerned: medical researchers, practitioners and students, and English for medical purposes (EMP) teachers, researchers and students. (Contains 1 figure and 5 tables.)