The recruitment and retention of students interested in STEM pursuits (science, technology, engineering, and mathematics) is a national priority obstructed by a lack of relevant measures. We developed a set of assessment devices applicable to program evaluation as well as the identification of STEM interested students and their self-efficacy levels. In this article, we report the psychometric properties of two interest and two self-efficacy measures of STEM-related activities and occupations. Exploratory factor analyses conducted on each measure with a randomly selected half of the sample (n = 213) resulted in one general STEM factor. Confirmatory factor analyses were conducted on shortened versions of the tests for the remaining half of the sample (n = 190). Goodness-of-fit indices all supported the one-factor model. Applications of the instruments to STEM assessment and education are discussed.