This chapter provides a review of studies assessing the changes that occur in different memory systems and processes from young adulthood to old age. The evidence reviewed indicates interesting differential patterns of development in adulthood and old age that depend on different factors, including the task and the memory type involved. Several theoretical accounts at different levels of generality that have been suggested to explain the age-related patterns of memory development, and especially of episodic memory deficits, are discussed. Finally, a unified approach is suggested that may serve as a departure point to further advance our knowledge of age-related changes in memory.