Textiles are used in many industrial applications, especially in papermaking. During the pressing of paper, felts are used to recover the water expressed from the wet sheet. To improve this operation, felt structures have to be characterized. X-ray microtomography is a powerful tool for reconstructing the complex organization of such fibrous materials. This method is first described, then examples of measurements are shown and discussed. This nondestructive technique appears to be an excellent tool for investigating woven and nonwoven structures. The fine description of the structure permits the characterization of structural parameters and numerical modeling of physical phenomena of this true three- dimensional structure.