Dr. Sydney A. Asdell was the first Ph.D. student of F.H.A. Marshall at Cambridge University. Dr. Asdell had an encyclopedic memory. This served him well in teaching and research, and especially in compiling and organizing his book "Patterns of Mammalian Reproduction." This book is a classic compendium of the major facts of reproduction in many species. This brief biography summarizes his life and scientific career.