We tested the notion that action observation engages learning processes and mnemonic representations overlapping with those engaged in actual performance. An identical number of training instances, actual performance, or observation, was afforded on a finger opposition sequence task. Both training modes resulted in immediate gains in performance, as well as in robust delayed, "off-line," gains, indicating post-training consolidation. However, the expression of delayed gains could be blocked by the subsequent performance of a second sequence (post-training interference), but not by its observation. The mnemonic representations of "how-to" knowledge acquired from actual or observed movement may not overlap.