My current research centers on the theory of stellar evolution, especially on methods of testing the validity of its details. I am working as part of an international collaboration to determine accurate fundamental astrophysical data about stars in eclipsing binary and multiple star systems. The types of data we are able to provide include orbital parameters, masses, radii, luminosities, and internal structure of the stars. In order to obtain these data, we need to measure both the brightness as a function of time (the light curve) of the eclipsing binary and the radial velocities of both stars as a function of time (the RV curve). It is possible to measure light curves of these eclipsing binaries with a relatively small telescope. For this purpose we are using telescopes in Chile and at the University of Arkansas Droke Observatory near Fayetteville. Radial velocities are derived from spectra which must be obtained with larger telescopes. Telescopes at McDonald Observatory in Texas and at Kitt Peak National Observatory in Arizona have been used in an ongoing program to obtain digital spectra of our program stars. Radial velocities are extracted from the spectra with main-frame computers on campus. Numerical models can be fitted to the photometric and spectroscopic data to derive fundamental astro-physical parameters such as the masses and radii of the stars. We can often measure these data to an accuracy of 1% or better, and new techniques promise to improve this accuracy to much higher levels, perhaps to better than 0.1%. At this level of accuracy the observations can serve as a critical test of theories of stellar evolution - theories which cannot match the observations must be rejected. Our efforts are directed to the task of testing our current theories at the highest levels of accuracy attainable.