As part of our systematic study on the curing reaction of novolac resins with hexamethylenetetramine (HMTA), the reactions between 2,6-xylenol (a model phenol) and HMTA, and the thermal decomposition of their first-formed products bis- and tris(4-hydroxy-3,5-dimethylbenzyl)amines have been studied by C-13 and N-15 n.m.r. spectroscopy. The thermal decomposition of bis- and tris(4-hydroxy-3,5-dimethylbenzyl)amines results in the formation of para-para methylene linkages between rings. Other products are formed during the process, and only minor amounts of these remain after heating to 205 degrees C/4 h; however, these minor products provide important information on the reaction pathways. The possible reaction mechanisms/pathways for the formation of cross-linked networks from para-hydroxybenzylamine intermediates are postulated on the basis of these structural changes.