Special Topic Brain, Behavior and Evolution 1997, Vol. 50, No. 4 Since there is only the most limited fossil record of sensory systems available, much of the evolutionary history of vertebrate sensory systems has to be extrapolated from a thorough knowledge of comparative sensory biology. The papers in this publication illustrate the two contrasting themes of conservation and innovation in the evolution of structures and functions of sensory systems. Leading experts apply their knowledge of comparative sensory biology in an attempt to add to our understanding of the evolution of vertebrate sensory systems. Readers will find many new ideas and fresh insights into how sensory systems may have evolved.