C-13-nuclear magnetic resonance (NMR) spectroscopy was employed to study the linkages in three commercial fully methylolated melamine-formaldehyde (HMMM) resins and their partially self-condensed resins by acid catalysis, in order to probe the structures linking melamine units. Distortionless enhancement by polarization transfer (DEPT) experiments show that the partially self-condensed resins contain both methylene ether (drop NCH2OCH2N drop) and methylene (drop NCH2N drop) linkages between melamine units. The extent of these linkages were estimated by quantitative C-13-NMR spectroscopy using inverse gated decoupling techniques. The results show that the ratios of methylene ether and methylene linkages to the triazine moiety vary from resin to resin.