The effect of organically modified clay (organoclay) on the cross-linking of a high performance thermoset resin-diallylbisphenol A (DBA) modified bismaleimide (DBA/BMI), is studied using rheometry and FTIR spectroscopy. The validity of the Winter-Chambon criterion was examined for the cross-linking of these filled polymers. Physical gels have been formed prior to the chemical cross-linking with 3.0 and 5.0% organoclay 1.30TC. The physical properties of the gel, including the loss tangent, critical relaxation exponent and the gel strength in the absence and presence of organoclay, were investigated and the results indicated that organoclay showed a great effect on the physical properties of the gel. Organoclay reduced the gel time but decreased the degree of the cross-linking slightly at the gel point, as revealed by the FTIR spectroscopy. The dispersion of organoclay also affected the gel characteristics. More elastic and stronger gel can be obtained when organoclay was better exfoliated. When another type of organoclay Cloisite 30B was used, results indicated that the nature of organoclay had a considerable effect on the cross-linking in the polymer system. (c) 2004 Published by Elsevier Ltd.