The reactions of 2,4-xylenol and 2,6-xylenol, with bis- and tris(4-hydroxy-3,5-dimethylbenzyl)amines derived from the reaction of 2,6-xylenol with hexamethylenetetramine (HMTA) were studied as models for the curing of novolac resins. The structural changes during the process were examined by C-13 and N-15 n.m.r. spectroscopy. The results indicate that reactions between bis- and tris(4-hydroxy-3,5-dimethylbenzyl)amines and 2,4-xylenol (containing an ortho reactive sites) produce para-para, ortho-para, and ortho-ortho methylene linkages between phenolic rings via a number of reaction pathways. Heating bis- and tris(4-hydroxy-3,5-dimethylbenzyl)amines with 2,6-xylenol only produces para-para methylene linkages, but the reactions occur at relatively low temperatures compared to those of the thermal decomposition of the bis- and tris(4-hydroxy-3,5-dimethylbenzyl)amines. Numerous side-products were observed during the process, but most of these can be further reacted or oxidised to form methylene linkages, and only minor amounts remain after heating to 205 degrees C. Reaction mechanisms and possible reaction pathways are postulated based on structural changes.