Patterns of sequential effects in serial 2-choice reaction-time tasks have been explained by 2 processing mechanisms, automatic facilitation and subjective expectancy, depending on the response-to-stimulus interval (RSI) and stimulus–response compatibility. Both mechanisms were localized in stimulus- or response-related processing stages with 4-stimulus 2-response experiments. Stimuli were presented on the corners of a square and keys were left–right or up–down. Subjective expectancy, appearing at long RSI, was systematically response related. Automatic facilitation, appearing with short RSI, shifted toward stimulus-related processes with noncompatible mappings. The results support the idea that automatic facilitation is related to structural bottom–up processes and is mainly located in stages that gain most from a facilitatory effect, whereas subjective expectancy needs a minimum time and therefore appears in late, response-related stages.