A job analysis was conducted to define the knowledge important for entry-level earth and space science teachers. The results will be used to guide the development of new test content specifications for the Praxis Series Earth and Space Science assessment. A draft domain was constructed from existing test content specifications, national standards, and feedback from item writers, examinees, and standing committees. A national advisory committee (NAC) of 12 teachers and college faculty reviewed and modified the draft domain to reflect the knowledge they believed was important for safe and effective practice and needed at time of entry into the profession. The revised domain consisted of 58 statements clustered within six major categories: (a) Basic Scientific Principles and Processes, (b) Tectonics and Internal Earth Processes, (c) Earth Materials and Surface Processes, (d) History of the Earth and Its Life-Forms, (e) Earth’s Atmosphere and Hydrosphere, and (f) Astronomy. Survey responses of 304 educators provided independent evidence of the importance of the domain. Respondents judged each knowledge statement on a scale ranging from 1 (not at all important) to 5 (extremely important). A total of 54 knowledge statements had mean ratings above 3.50 in the aggregate sample and for subgroups containing more than 30 respondents. The results indicate that these 54 statements may be considered appropriate for guiding the development of new test content specifications for the Praxis Earth and Space Science assessment.