Studied the role of rewards in self-imposed and externally imposed delay situations with 111 3rd graders. Time estimation was used as the index of delay frustration, with greater time estimates being interpreted as indicating greater frustration. In self-imposed delay situations, Ss produced longer time estimates when a reward was contingent on the delay than when no reward was offered. Furthermore, Ss estimated the delay to be longer in the self-imposed delay when the offered reward was physically present than when it was absent. When the delay was externally imposed, with no opportunity for self-termination, the offer of a contingent reward and the physical presence of reward reduced delay time estimates. Results also indicate that Ss high and low in the ability to tolerate delay frustration were not equally able to cope with both types of delay.