A micro-digestion procedure for the determination of neutral (NDF) and acid detergent fiber (ADF) employing 0.35 g of sample was developed. Four roughages and corn grain were digested by the standard Van Soest macro acid and neutral detergent fiber methods, and by the micro method. Differences between two-thirds of the means for NDF and ADF, as determined by the two methods, were statistically significant (P < 0.05). Absolute differences between means for all samples analyzed were small, with a range from 2.82 to 1.41 percentage units for NDF and 0.85 to 0.14 percentage units for ADF. Neutral detergent fiber determinations of corn grain were completed without filtration problems when the micro-digestion method was employed, in contrast to the difficult filtrations encountered with the macro method. Standard deviations of means for samples digested by the micro method were small except for corn grain.