Ph.D. / The main objective of this study was to investigate the presence, variations and the fate of lipophilic extractives during all the stages in the dissolving pulp production process. Lipophilic wood extractives which include fatty acids, sterols, hydrocarbons, steroid hydrocarbons and ketones are organic compounds present in the wood and dissolving pulp which are soluble in organic solvents. Their presence in wood and pulp has negative effects on both the pulping process and the quality of the produced dissolving pulp. Comparison of two Eucalyptus species (E. grandis and E. dunnii) at three different sites (Richmond, Umvoti and Ixopo in KwaZulu-Natal Province, South Africa) revealed that lipophilic extractives were higher in E. dunnii than in E. grandis in all the sampled sites and that the woods at the Ixopo site were found to have the highest amount of lipophilic extractives. The quantitative variation of lipophilic extractives in wood was found to be significantly affected by respective sites and tree species. The principal component analysis (PCA) model, which was used to correlate soil parameters and amount of lipophilic extractives in woods per each site, revealed that high amounts of lipophilic extractives were found in trees grown at sites with a high composition of clay soil and organic matter. Thus if the industry is to avoid the high levels of lipophilic extractives in wood, sandy sites should be the choice to grow the trees. Partial least squares (PLS) modelling revealed that sterols and saturated fatty acids significantly influence the quality parameters (Kappa number, viscosity, copper number, cellulose yield and retained carbohydrates) of dissolving pulp, whereas unsaturated fatty acids and unsaturated sterols in particular were found to positively correlate with the Kappa number, thus affecting its measurement.The main objective of this study was to investigate the presence, variations and the fate of lipophilic extractives during all the stages in the dissolving pulp production process. Lipophilic wood extractives which include fatty acids, sterols, hydrocarbons, steroid hydrocarbons and ketones are organic compounds present in the wood and dissolving pulp which are soluble in organic solvents. Their presence in wood and pulp has negative effects on both the pulping process and the quality of the produced dissolving pulp. Comparison of two Eucalyptus species (E. grandis and E. dunnii) at three different sites (Richmond, Umvoti and Ixopo in KwaZulu-Natal Province, South Africa) revealed that lipophilic extractives were higher in E. dunnii than in E. grandis in all the sampled sites and that the woods at the Ixopo site were found to have the highest amount of lipophilic extractives. The quantitative variation of lipophilic extractives in wood was found to be significantly affected by respective sites and tree species. The principal component analysis (PCA) model, which was used to correlate soil parameters and amount of lipophilic extractives in woods per each site, revealed that high amounts of lipophilic extractives were found in trees grown at sites with a high composition of clay soil and organic matter. Thus if the industry is to avoid the high levels of lipophilic extractives in wood, sandy sites should be the choice to grow the trees. Partial least squares (PLS) modelling revealed that sterols and saturated fatty acids significantly influence the quality parameters (Kappa number, viscosity, copper number, cellulose yield and retained carbohydrates) of dissolving pulp, whereas unsaturated fatty acids and unsaturated sterols in particular were found to positively correlate with the Kappa number, thus affecting its measurement. Viscosity of pulp which is an important quality parameter was also found to be positively influenced by sterol residues, whereas the reducing properties of pulp were found to be affected by sterols and saturated fatty acids with a carbon chain length of less than C20.