We present MMC, a model checker for mobile systems specified in the style of the -calculus. MMCs development builds on that of XMC, a model checker for an expressive extension of Milners value-passing calculus implemented using the XSB tabled logic-programming engine. MMC addresses the salient issues that arise in the -calculus, including scope extrusion and intrusion and dynamic generation of new names to avoid name capture. We show that logic programming provides an efficient implementation platform for model checking -calculus specifications and can be used to obtain an exact encoding of the -calculuss transitional semantics. Moreover, MMC is easily extended to handle process expressions in the spi-calculus of Abadi and Gordon. Our experimental data show that MMC outperforms other known tools for model checking the -calculus.