The interactions between hexamethylenetetramine (HMTA) and models for both poly(N-(hydroxyphenyI) maleimides) and phenol-formaldehyde resins have been examined. There is direct interaction between HMTA and the N-(hydroxyphenyI) succinimide and xylenols used as model compounds. When the model compounds both contain a free ortho position, four different benzoxazine derivatives are formed, that is, the succinimide-succinimide and xylenol-xylenol benzoxazines and the two ＇mixed＇ systems. The rate of reaction of HMTA with the mixed system was measured via C-13 nuclear magnetic resonance spectroscopy (n.m.r.). The relative rates of formation of the benzoxazine derivatives are dependent on the substitution pattern of the phenolic rings. Control over the interactions between HMTA and the models was achieved via selective masking of the phenolic groups using the thermally labile tetrahydropyranyl (THP) group.