This study attempts to explain accommodation, particularly aerial/aquatic accommodation, in the cetacean eye. Eyes from two species in particular were studied: the bottlenose dolphin, or Tursiops truncatus (12 eyes), and the sperm whale, or Physeter catodon (12 eyes). Investigation of the lens/iris diaphragm and suspensory apparatus of the lens was undertaken by measurement and dissection. Results from this study clearly indicate cetacean accommodation to be effected by lens movement, as opposed to lens deformation or changes in the pupillary diameter. The system here described would yield the possibility of excellent visual acuity both below and above water in these animals.