Economic choice entails assigning values to the available options and is impaired by lesions to the orbitofrontal cortex (OFC). Recent results show that some neurons in the OFC encode the values that monkeys (Macaca mulatta) assign to different goods when they choose between them. A broad and fundamental question is how this neuronal representation of value depends on the behavioral context. Here we show that neuronal responses in the OFC are typically invariant for changes of menu. In other words, the activity of a neuron in response to one particular good usually does not depend on what other goods are available at the same time. Neurons in the OFC encode economic value, not relative preference. The fact that their responses are menu invariant suggests that transitivity, a fundamental trait of economic choice, may be rooted in the activity of individual neurons.