The chemical structure of milled-wood lignins from Euca-lyptus globulus, E. nitens, E. maidenii, E. grandis, and E. dunnii was investigated. The lignins were characterized by analytical pyrolysis, thioacidolysis, and 2D-NMR that confirmed the predominance of syringyl over guaiacyl units and only showed traces of p-hydroxyphenyl units. E. globulus lignin had the highest syringyl content. The heteronuclear single quantum correlation (HSQC) NMR spectra yielded information about relative abundances of inter-unit linkages in the whole polymer. All the lignins showed a predominance of b-O-49 ether linkages (66–72% of total side-chains), followed by b-b9 resinol-type linkages (16–19%) and lower amounts of b-59 phe-nylcoumaran-type (3–7%) and b-19 spirodienone-type linkages (1–4%). The analysis of desulfurated thioaci-dolysis dimers provided additional information on the relative abundances of the various carbon-carbon and diaryl ether bonds, and the type of units (syringyl or guaiacyl) involved in each of the above linkage types. Interestingly, 93–94% of the total b-b9 dimers included two syringyl units indicating that most of the b-b9 sub-structures identified in the HSQC spectra were of the syringaresinol type. Moreover, three isomers of a major trimeric compound were found which were tentatively identified as arising from a b-b9 syringaresinol substruc-ture attached to a guaiacyl unit through a 4-O-59 linkage. Current address: Department of Fiber and Polymer Technology, a Royal Institute of Technology (KTH), SE-100 44 Stockholm, Sweden. heteronuclear single quantum correlation (HSQC); milled-wood lignin (MWL); pyrolysis-GC/MS; thioacidolysis; trimers.