There has been considerable debate about whether or not we need to distinguish between the acquisition of implicit-and, independently thereof, the acquisition of explicit-knowledge in sequence learning tasks. Proponents of the view that a unitary knowledge base is formed assume (a) that the knowledge acquired is explicitly available, and (b) that information about sequence fragments forms the core of this explicit knowledge. Both of these issues are addressed empirically in the present article. In two experiments, an adapted process dissociation procedure and a suitable measurement model were used to separate recollective (explicit) and fluency-based (implicit) memory processes in a sequence learning task. Experiment 1 demonstrated that fluency-based processes came into play much later than recollective processes. Such recollective processes have been conceptualized as being based on simple knowledge about sequence fragments or chunks. Indeed, Experiment 2 showed that recollective processes are more likely to contribute to sequence judgements if chunks are readily available at test than if they are not. Together, these results are in line with the view that the learning of an event systematicity can be conceived of as the memorization of chunks of events that support both the speedingup of reaction times to systematic events and explicit, recollective memory processes even after relatively little training.