There is considerable national interest in STEM initiatives, but yet there is little discussion concerning what STEM means in terms of a curriculum concept to be applied to school programming. This article focuses on STEM as a curriculum concept. First, STEM programming is discussed in terms of separate subjects, correlated and broad fields curriculum models. The issue of subject structure is examined. A distinction also is made between the four STEM subjects in terms of formal and applicative uses of knowledge. Second, some practical programming issues are discussed. These include the almost exclusive focus on science and math to the exclusion of technology and engineering; the challenge of serving multiple student populations; and the issue of what to do with the "T" in STEM. A concluding section suggests ways that the STEM initiative can be conceptualized in order to realize its considerable potential to achieve curriculum reformulation. (Contains 2 figures.)