Pretreatment is an important step in the biochemical conversion of biomass to biofuels.  Different types of thermo-chemical pretreatments are used to open up the biomass structure and increase cellulose enzymatic digestibility.  The effectiveness of different pretreatment methods and conditions can be compared by measuring the sugar compositions of the pretreatment liquors.  At National Renewable Energy Laboratory (NREL) we have adapted wood feedstock compositional analysis methods for use on pretreatment liquors.  These measure the monomeric sugars and total sugars (after 4% acid hydrolysis) released from the biomass into solution during pretreatment.  We will report the variability of these methods on a dilute-acid pretreated corn stover liquor sample run by six analysts in 14 batches of six replicates and in two NREL laboratories.  Suggestions for method improvement will be offered.