Polyaralkyl-phenolic resin, whose commercial name is Xylok, is in the class of high-performance resins, but its slow reactivity and brittleness limit its application in modern industry. Many efforts have been made to modify Xylok, but have not satisfactorily resolved these problems. In this paper, the authors employ allylization to improve properties of Xylok. The allyl Xylok can be thermally polymerized by itself or with bismaleimide (BMI) as a good comonomer. The reactivity of the allyl Xylok/BMI resin system was investigated by gel characteristics and differential scanning calorimetry (DSC). The thermal stability of the cured copolymer was evaluated by dynamic thermogravimetric analysis (TGA). No weight loss was observed when the copolymer was heated to 490-500°C in a nitrogen atmosphere. The hot/wet resistance properties of the cured allyl Xylok/BMI resin were investigated by aging it in boiling water. After aging for 100 h, water absorption and heat deflection temperature (HDT) were 2.3% and 280°C, respectively. The properties of the glass fiber reinforced compression molding materials (GCM) based on the copolymer of the allyl Xylok/BMI matrix resin system are also discussed. 0 1996 John Wiley & Sons, Inc.