In this work, direct probe mass spectrometry, DP-MS, method was applied to investigate the characteristics of polymer/organoclay composites. For this purpose organically modified montmorillonites involving four different alkyl quaternary ammonium salts were incorporated into polylactide, poly(methyl methacrylate) and polyethylene matrices. The morphology of the composites were first analyzed by x-ray diffraction, XRD, and transmission electron microscopy, TEM, measurements. The temperature regions at which the organic modifier was lost during the pyrolysis of the organoclays and the polymer/organoclay composites were correlated with inter-layer spacing of the clay layers. It has been determined that the loss of organic modifier shifted to lower temperatures as the interlayer-spacing increased. As a consequence of broader inter-layer spacing, the extent of intercalation was improved leading to an increase in thermal stability of the matrix polymer. The results clearly showed that the DP-MS technique supplies strong evidences for the extent and type of dispersion of clay layers in the polymer matrices. In addition the technique allows identification of possible interactions between the polymer and the organic modifier.