The determiners in English include three categories: predeterminers, central determiners, and postdeterminers. The focus of the present study is the central determiners because they comprise the largest group and because a minimum of one central determiner is required in the generation of any noun phrase. Furthermore, the central determiners have the characteristic of mutual exclusivity, i.e., only one may occur at a time. These determiners include the articles (a(n), the, and zero article), the possessive pronouns (e.g., my, his, their) and genitive's (the doctor's, the planet's), the demonstrative pronouns (e.g., this, those), and the determiners some/any, each/every, either/neither, and no. The determiners are an important aspect of academic discourse because of the frequency with which they occur. Certain determiners, particularly the definite and indefinite articles, cause students considerable difficulty not only because of the opacity of the rules of usage but also because native-English-speaking readers are rather intolerant of their misuse. The occurrence of every central determiner in two full research articles (RAs) in eight different disciplines (biology, chemistry, computer science, engineering, geology, mathematics, medicine, physics, and, as a control, applied linguistics) was analyzed using a method tested and refined in an earlier pilot study of determiner usage in several genres. In that study, determiners were found to make up the largest percentage of the total word count in the science magazine Science News (21%) and the smallest percentage in Graham Greene's novel The Tenth Man (14%); furthermore, the articles comprised the largest percentage of the determiners in Science News (89%) and the smallest percentage of Shakespeare's Julius Caesar (57%), suggesting that the discourse of science may utilize a greater degree of "determination" than other discourse communities. Results of the present study showed that the RAs are remarkably similar as far as the percentage of determiners comprising articles is concerned and that the RAs have the highest percentage of articles vs. other determiners compared to other genres in the pilot study, which suggest that the RA genre may be characterized by this feature. The results also show which of the determiners are more prevalent and therefore worthy of inclusion in any attempt to initiate students into the written discourse of scientific research articles. The manner in which determiners are used in scientific English will be of interest to students of EST as well as genre analysts trying to determine the nature of written discourse in particular genres. (Contains 3 tables, 14 figures, and 3 endnotes.)