The purpose of this compendium is to provide an overview on the current status of STEM instrumentation commonly being used in the U.S and to provide resources useful to research and evaluation professionals. The information contained within is heavily dependent on information available on existing websites. For each instrument we provide information on the constructs/variables that are measured, the target audience of the instrument, the subject domains assessed, information on obtaining the instrument, and related documents about reliability and validity evidence when it could be located. While the information about reliability and validity evidence is provided, we highly recommend that anyone intending to use an instrument consult the Standards for Educational and Psychological Testing published jointly by the American Educational Research Association, the American Psychological Association, and the National Council on Measurement in Education (1999), to ensure proper deployment, piloting and evidence accumulation for a particular research or evaluation application and study population. These standards are in the process of being revised as of November 2012.