In the early visual pathway, the lateral geniculate nucleus (LGN) is the major relay station from where visual information is transmitted to the cerebral cortex. How LGN neurons code luminance remains unclear. We addressed the issue by presenting the luminance stimuli that were continuously changing at 50 Hz to neurons of cat LGN. The rapid changes in luminance enhanced responses of LGN neurons to uniform stimuli. Responses of a neuron to the luminance stimuli were sorted using the reverse correlation algorithm and luminance response function (LRF) was extracted from the responses. Most neurons (81%) had either increase or decrease LRFs, and the remaining neurons (19%) had V-shape LRFs. The relationships between the response magnitudes to luminance increments and decrements of uniform stimuli and those to ON and OFF stimuli presented inside receptive field (RF) revealed that the increase, decrease, and V-shape LRFs of most neurons (83%) were determined by the relative strength of ON-OFF responses of their RFs, and the LRFs of the other neurons (17%) were related to the excitation-inhibition interactions between RF ON-center (or surround) and OFF-surround (or center) of RF structure. The results unveiled the neural mechanisms underlying the responses of LGN neurons to uniform luminance.