Is implicit learning an independent and automatic process? In this paper, ! attempt to answer this question by exploring whether implicit learning occurs even despite the availability of more reliable explicit information about the material to be learnt. I report on a series of experiments during which subjects performed a sequential choice reaction task. On each trial subjects were exposed to a stimulus and to a cue of varymg validity which, when valid, indicated where the next stimulus would appear. Subjects could therefore optimize their performance either by implicitly encoding the sequential constraints contained in the material or by explicitly relying on the information conveyed by the cue. Some theories predict that implicit learning does not rely on the same processing resources as involved in explicit learning. Such theories would thus predict that sensitivity to sequential constraints should not be aftectcd by the presence of reliable explicit information about sequence structure. Other theories, by contrast, would predict that implicit learning would not occur in such cases. The results suggest that the former theories arc correct. I also describe preliminary simulation work meant to enable the implications of these contrasting theories to be explored.