The effect on shop performance of granting customer requests for setting earlier clue dates on jobs already in process in the shop was investigated, via computer simulation, for a five-machine pure job shop. One-replicate, two-way classification (with interaction) and contrasts were used to examine the effect on various measures of shop performance of (1) four levels of mean interarrival time, A, and (2) five levels of the percentage of all jobs with CKEDD (customer requested earlier due date) status, T. Regression equations were developed for each performance measure in terms of the independent variables, A and T.