This research shows that people can unconsciously initiate and follow arithmetic rules (e.g., addition). Participants were asked to detect whether a symbol was a digit. This symbol was preceded by 2 digits and a subliminal instruction: "add" or a control instruction. Participants were faster at identifying a symbol as a number when the symbol was equal to the sum of the 2 digits and they received the instruction to add the digits, suggesting that people can unconsciously solve arithmetic problems. Experiments 2 and 3 replicate these findings and demonstrate that the underlying processes can operate when the to-be-added digits are not perceived consciously. Thus, the unconscious can do (at least simple) arithmetic, such as addition. (Contains 2 figures and 2 footnotes.)