Visualization of porosity in three dimensions (3D) is critical to a detailed under-standing of the microstructure and properties of powder metallurgy (PM) steels. Two techniques are described to characterize porosity in 3D: serial sectioning and X-ray tomog- raphy. Both techniques can be used to visualize porosity, and to quantify pore fraction and the degree of pore interconnectiuity. The use of image-based finite element simulations, using two-dimensional (2D) images of the microstructure, is also described. This is an invaluable tool in correlating pore structure with the mechanical properties of the steel.