Suspended sediment concentration was monitored in a large discharge vent at the northern terminus of the Matanuska Glacier. Samples were obtained every two hours during the period July 28 through August 26, 1999, using an automated sampler. Sediment concentrations were determined by standard filtration techniques. The data show diurnal fluctuations in suspended sediment concentration, with the daily maximum concentrations typically occurring in the early evening and minimum concentrations in the late morning. The highest sediment concentration of 2.6 g/L occurred on August 2, and the lowest sediment concentration of 0.37 g/L occurred on August 23. No major rain events occurred during this time period. The average suspended sediment concentration during the sampling interval was 1.0 g/L. As the ablation season progressed, there was a general decrease in suspended sediment concentrations at this vent. Water discharge also fluctuated diurnally, with peak discharge usually preceding peak sediment concentration by 1-4 hours, suggesting temporary storage of sediment in the subglacial system each day. The diurnal fluctuation of suspended sediment concentrations measured at the vent is similar to and in phase with concentrations measured at another major subglacial discharge site on the western end of this glacier terminus. Suspended sediment concentrations measured at this glacier are similar to those measured by other researchers at smaller, alpine glaciers in the Alps, which suggests that glacier size has little control on the sediment concentrations in subglacial discharge.