The present study used a concurrent-chains schedule to examine the effect of reward amount on delay discounting in rats. Delay periods defined by fixed-interval schedules in the terminal links were fixed at 2 s in one alternative and varied in the other alternative across five conditions ranging from 2 s to 40 s. The reward amounts were varied across three conditions by manipulating the number of food pellets (1 pellet vs. 1 pellet, 5 pellets vs. 1 pellet, and 5 pellets vs. 5 pellets). The discounting rate estimated with a modified hyperbolic function was higher in the smaller reward amount condition than in the larger reward amount conditions. This finding indicates that in animals the rate of delay discounting decreases as the reward amount increases.