Several studies have found decision-making-related value signals in the dorsolateral prefrontal cortex (DLPFC). However, it is unknown whether the DLPFC plays a causal role in decision-making, or whether it implements computations that are correlated with valuations, but that do not participate in the valuation process itself. We addressed this question by using repetitive transcranial magnetic stimulation (rTMS) while subjects were involved in an economic valuation task involving the consumption of real foods. We found that, as compared with a control condition, application of rTMS to the right DLPFC caused a decrease in the values assigned to the stimuli. The results are consistent with the possibility that the DLPFC plays a causal role in the computation of values at the time of choice.