We report on the design of both transmission and fluorescence x-ray-absorption spectroscopy cells suitable for in situ characterization of heterogeneous catalysts. The heart of both cells is a quartz tube used to house the catalyst sample. Both cells allow in situ x-ray-absorption fine-structure (XAFS) data to be recorded from -196 to 825 degrees C using a wide range of gas flows at atmospheric pressure. Excellent temperature control is demonstrated with both designs. XAFS data can be recorded over a wide x-ray energy range (2.1-29 keV). These designs are simple, robust, relatively low cost, and, moreover, are reliable and easy to operate. All of the critical components of the transmission reactor can be purchased commercially, with little machining required. The design of the fluorescence reactor requires access to a skilled glass blower. (c) 2006 American Institute of Physics.