ABSTRACT. The syringyl/guaiacyl (S/G) ratio of Eucalyputs grandis lignin was determined and its relation with kraft pulping parameters was studied. Twenty one wood samples obtained from 10-year-old trees grown in the same place were analyzed using Py-GC-MS to determine the syringyl/guaiacyl (S/G) ratio. The samples were pulped to the same final lignin content (Kappa number 18) obtaining pulp yields between 48.8% and 54.3%. Relationships were observed between pulp yield and S/G ratio (r = 0.51) also between alkali charge used in pulping and S/G ratio (r = -0.60). © 2014 Elsevier B.V.