This study reports a simple and low-cost preparation method for nearly exfoliated polyamide 66 (PA66)/montmorillonite (MMT) nanocomposites. Polymerizable methyl methacrylate (MMA) is used as cointercalation agent to take advantages of both in-situ polymerization and melt mixing. Two preparation approaches, either direct melt compounding or dilution from a master-batch, are investigated. The nano-scale dispersion of organo-MMT (OMMT) in PA66 is revealed by X-ray diffraction and transmission electron microscopy. PA66/MMT nanocomposites having superior mechanical properties and heat distortion temperature (HDT) can be obtained by either of the two preparation approaches on condition that excess MMA, which is on the surface of PA66/OMMT is removed by ventilation before melt compounding. (C) 2007 Wiley Periodicals, Inc.