The entry on "realism" in Baldwin's Dictionary notes that the term has two significant but distinct meanings in philosophy. In the older sense, it is a "logicalmetaphysical" theory about the nature of universals and their relation to particulars. In the more modern sense, it is an "epistemological-metaphysical" theory which holds that "reality exists apart from its presentation to, or conception by, consciousness." Russell was a realist in both these senses. In this paper, I focus, for the most part, on the development of Russell's realism in the second sense from 1910 to 1915. After abandoning idealism in 1901, Russell became, and professed to remain, a realist. But a consistent picture of what he took realism to entail is not easy to come by. Part of the problem is that Russell used the term "realism" in several different senses throughout the period of interest. In Our Knowledge of the External World, we can discern at least four distinct notions of "real". In the following, I examine what Russell has to say about the concept of reality and its correlate "existence" especially with regard to the question of determining the respective ontological status of sense-data and physical objects. It is sometimes suggested that Russell abandoned realism, at least with respect to physical objects, during his constructivist phase. I think this is a mistake based on a failure to appreciate the multidimensionality of Russell's view of "realism". I do not, however, pretend that what I have to say here is the final word. It is, at best, a good beginning. I shall proceed by examining, in order of publication, five key works by Russell during the period: "Knowledge by Acquaintance and Knowledge by Description", The Problems ofPhilosophy, Our Knowledge, "The Relation of Sense-Data to Physics"~ and "The Ultimate Constituents of Matter". The primary object is to try to tease out Russell's position vis-a-vis scientific realism, which I here take to be, minimally, the view that the theoretical entities of well-confirmed theories exist and are real.