Three experiments investigated the role of processing sequence knowledge in negative transfer within multistep cognitive skills. In Experiments 1 and 2, more training resulted in higher error rates when new processing sequences that resembled familiar ones were introduced in transfer. Transfer error responses were executed with the same speed as correct responses to familiar sequence trials, and the errors appeared to be undetected by the performers. Experiment 3 tested whether the effects of sequence learning were attributable to explicit or implicit knowledge of processing sequences. Evidence favored the implicit learning interpretation. Findings are discussed in relationship to earlier demonstrations of the einstellung effect and to current taxonomic theories of human error.