The implementation of a gas-source mass spectrometer and stable isotope extraction lines in our undergraduate curriculum provides students with hands-on experience in instrument-based laboratory exercises. In our geoscience program, we have designed, developed, and implemented stable isotope lab exercises for use in our Surface Water Hydrology, Petrology, Geomorphology, Groundwater, and Geochemistry courses. In our atmospheric science program, we have designed, developed, and implemented lab exercises for use in our Global Climate Change, Elements of Air Pollution, and Principles of Dynamic Meteorology courses. The developed exercises are an adaptation of a stable isotope lab exercise used at Dartmouth College (J. Geosc. Ed. 45:157-161). Students are involved in designing experiment(s), collecting samples, extracting stable isotopes of carbon and oxygen from samples, making measurements on a mass spectrometer, interpreting data, and writing reports. We are adapting cooperative learning techniques that are being used successfully in chemistry laboratories (J. Chem. Ed. 71:141-143) by structuring the exercises so that students work in small groups during multi-week lab exercise(s). Such a learning environment improves the educational experience of all students (The Teaching Professor 4:1-2) with particular emphasis on increasing female participation and involvement (Teaching of Psychology 20:7-13). These active-learning exercises allow students to participate directly in the process of scientific inquiry from formulation of the problem to presentation of results. The activities also help students appreciate the importance of stable isotope geochemistry to the earth and atmospheric sciences. Students work with faculty in formulating scientific questions relevant to a given course. This approach is a modification of guided-inquiry-based experiments that are used in chemistry labs (J. Chem. Ed. 75:470-471). The questions focus primarily on geologic, environmental, and/or atmospheric issues that are related to the urban environment surrounding Saint Louis University providing a sense of ownership for the students. During the course of the project, students collect and prepare samples for analysis and make extractions and mass spectrometric analyses. They graph their data and incorporate the data from other groups in order to document spatial or temporal trends, and make calculations to determine specific parameters relevant to the question(s) being addressed (e.g., origin of isotopes, extent of fluid-rock interaction, temperature of mineral formation). Students write a report and present their results to the rest of the class. By being involved in the project from beginning to end, students gain a deeper appreciation for science and the processes involved in scientific inquiry.