Previous work has shown that detectability of motion is better when the observer knows ahead of time the direction of that motion ("certainty") than when he does not know the direction ("uncertainty"). We now report attempts to reduce this performance decrement associated with direction uncertainty. In these experiments, a briefly flashed, oriented line cued the observer to the direction of motion that might occur. When the cue appeared before the moving target, detectability increased; when the cue appeared after the moving target, performance dropped below that for no cue at all. In addition, we examined the effect of cue reliability, varying the relation between cue orientation and actual direction of target motion. The more accurate the cue is, the larger the performance increment. When the cue indicated a direction more than 90 deg from the actual target direction, performance was worse than when there was no cue. Results are discussed with regard to the feasibility of reducing uncertainty in real-world situations. © 1981 Psychonomic Society, Inc.