Implicit learning of a series of new verbal associations was studied in four experiments. The first two experiments demonstrated that learning of a repeating sequence of verbal stimuli may occur without awareness, but only when the stimulus-response mapping requires an attention-demanding activity: Subjects who were unaware of the sequence learned when instructed to categorize the stimuli, but not when instructed simply to read them. However, in both situations, unaware subjects performed no better than untrained control subjects in expressing their knowledge of the sequence explicitly. In Experiments 3 and 4, subjects showed implicit learning when the task involved either motor responses to verbal stimuli or verbal responses to spatially arranged stimuli. These findings are discussed in terms of the conditions under which implicit learning can be obtained. First, they demonstrate implicit learning of a set of new associations in the verbal domain. Second, the data suggest that attention is important in implicit learning. Finally, the degree of interitem organization that is familiar preexperimentally seems to partially determine the amount of implicit learning.