This thesis summarizes an investigation into the need for removing extractives from herbaceous biomass feedstocks prior to their chemical characterization. Switchgrass (Panicum virgatum), was used in this study as a representative herbaceous biomass feedstock. The influence of extractives on the chemical analysis of switchgrass was done by comparing the composition of native switchgrass and solvent-extracted switchgrass preparations. Solvent-extracted switchgrass was prepared by extracting the native feedstock with either 95% ethanol, hot water or sequentially with ethanol and then water. Each of the feedstocks was analyzed for glycans, Klason lignin, acid soluble lignin, protein, ash, acetic acid and uronic acids. The results demonstrate that the extractives in native switchgrass significantly interfere with the analysis of Klason lignin. The lignin content of the feedstock was overestimated if the extractives were not removed prior to the analysis. The extractives in switchgrass did not affect glycan analyses. However, some soluble sugars are removed from the feedstock during the solvent extraction process. Total extractives removed by ethanol, water and ethanol/water amounted to 9.74%, 16.42%, and 19.11% of the feedstocks total solids, respectively. These amounts of extractives increased Klason lignin values by 4%, 4.5%, and 6.5% (on a wt percent of total solids), respectively. Most of the extractives in switchgrass are water-soluble and approximately one-quarter of these extractives measure as Klason Lignin. The removal of the water soluble extractives from the feedstock improved the mass closure values for the feedstock's summative analysis. Successive ethanol and hot water extraction has successfully removed most of the extractives in switchgrass yielding 100.4% mass balance. The recommended approach for the analysis of herbaceous biomass feedstocks will include sequential 95% ethanol and hot water extraction followed by chemical analysis on both the preextracted substrate and the extractives obtained from that substrate. / Graduation date: 1996