With the increased utilization of whey powders in food products there is a need to investigate the storage stability of whey powders. The objectives were to determine the effects that compositional factors of whey powders had on the Maillard reaction during storage. The Maillard reaction is the major deteriorative reaction limiting the shelf-life of whey powders. Eight commercial whey powders were stored at accelerated storage conditions (35°C) and at five different water activities, a_ws, (0.32, 0.44, 0.52, 0.63, and 0.74) for up to 120 days. Small quantities of the hydrolyzates of lactose- glucose and galactose (less than 2% dry wt.) caused a sizable increase in the relative rates of the Maillard reaction in whey powders. The relative rate of the Maillard reaction rate was determined by measuring brown pigment formation at 420 nm. Increasing the amount of nonprotein nitrogen (NPN) significantly increased the relative rates of the Maillard reaction in the whey powders. Increasing ash content had a positive but statistically insignificant effect on the Maillard reaction. The influence of water activity on the storage stability of whey powders was also investigated. Increasing the protein content of the whey powders increased the a_w, where the maximum rate of brown pigment formation was observed. In the highest protein whey powders (46% and 82%) however, the browning rate maxima shifted to lower a_ws. The loss in protein quality of the whey powders was determined by examining the loss of available lysine using the dye-binding method. Intermediate protein whey powders (31-40% protein) and unprocessed sweet dried wheys lost the greatest relative percentages of available lysine during the storage period. / Master of Science