pathology of multiple pregnancy collates case material from over 500 autopsies (including embryos) and 1200 placentas from twins, triplets, and higher multiples with selected literature on human multiple reproduction. it emphasizes important new concepts of pathophysiology and interpretation of less than ideal outcomes of multiple conception based on over 30 years experience in the field. aspects of perinatal pathology unique to twins and higher multiples are emphasized, with practical suggestions for the service pathologist, including items of potential medico-legal significance. controversial topics, such as the value of studies of concordance for diseases or malformations, and the significance of inter-twin anastomoses, are addressed and suggestions made for further investigation. a close working relationship between pathologists and clinical colleagues is encouraged by discussion of clinico-pathological correlations. and, the most recent discussions on mechanisms of twinning and genetic versus environmental influences on the development of twins are presented.