The STEM College-Going Expectancy Scale (STEM CGES) was developed and validated in two studies conducted during 2010 and 2011. The STEM CGES is a self-report instrument measuring college-going expectancy, specifically for science, technology, engineering, and mathematics (STEM) domains. In Study 1, 95 students in an urban high school completed an 11-item online questionnaire to measure college-going expectancy in STEM domains. Exploratory factor analysis (EFA) retained 6 out of the 11 items for inclusion. In Study 2, Confirmatory Factor Analysis (CFA) used data collected from 658 students in 31 urban, suburban, and rural high schools. The results provide strong evidence that the STEM CGES is a valid and reliable instrument for measuring college-going expectancy for STEM domains.