Structural asymmetries between the hemispheres are found in the human brain. Asymmetries in the auditory regions and in the Sylvian fissures are present even in the fetus. The Sylvian asymmetries may have existed in Neanderthal man and are found consistently in some apes. They may relate to right-left differences infunction. Thus, the striking auditory asymmetries could underlie language lateralization. The asymmetries in the frontal and occipital lobes and the lateral ventricles are correlated with hand preference. Anatomical asymmetries may help to explain the range of human talents, recovery from acquired disorders of language function, certain childhood learning disabilities, some dementing illnesses of middle life, and the evidence for behavioral lateralization in nonhuman primates.