A comparative survey shows that lamination is a basic feature of the mammalian dorsal lateral geniculate nucleus. Relay laminae receive input from the retina, project to the cerebral cortex and represent a complete hemiretina. They are distinguished from incomplete layers or leaflets and from groups of cells for which retinal connections or cortical projections are in question. The separate representations of the visual field in the relay laminae are precisely aligned so that each point in the visual field corresponds to a line passing from margin to margin through the nucleus and at right angles to the layers. Geniculate landmarks that provide clues regarding the organization of the layers are considered, and several experimental methods by which the laminar pattern can be displayed are evaluated.