Fertilization is defined as the process of union of two gametes, eggs and sperm. When mammalian eggs and sperm come into contact in the female oviduct, a series of steps is set in motion that can lead to fertilization and ultimately to development of new individuals. The pathway begins with species-specific binding of sperm to eggs and ends a relatively short time later with fusion of a single sperm with each egg. Although this process has been investigated extensively, only recently have the molecular components of egg and sperm that participate in the mammalian fertilization pathway been identified. Some of these components may participate in gamete adhesion and exocytosis, whereas others may be involved in gamete fusion. Here we describe selected aspects of mammalian fertilization and address some of the latest experimental evidence that bears on this important area of research.