We report two experiments that examine the effects of practice on the early facilitation and later inhibition of return (IOR) effects of cueing in detection and color-discrimination tasks. In the first experiment a short and a long SOA were mixed within a block of trials, so that there was temporal uncertainty. In the second experiment SOA was manipulated between subjects, to eliminate temporal uncertainty. Facilitation and IOR effects were obtained in the short and long SOAs respectively, in both detection and discrimination tasks, and they consistently decreased with practice. The cueing effects were more positive (i.e., bigger facilitation and smaller IOR) in the discrimination task than in the detection task. Cueing and practice effects were modulated by temporal uncertainty (Experiment 1 vs. Experiment 2). Our results go some way to resolving some of the contradictory findings in the literature. Keywords: IOR, facilitation, practice effects, spatial attention, orienting of attention, detection tasks, discrimination tasks.