Humans automatically categorize others in social perception. Some categorizations - race, gender, and age -- are so automatic that they are termed "primitive categories." As we categorize, we develop stereotypes about the categories. Researchers know much about racism and sexism, but comparatively little about prejudice based on age. The papers in this issue highlight the current empirical and theoretical work on understanding the origins and consequences of stereotyping and prejudice against older adults. With the aging baby boomer demographic, it is especially timely for researchers to work to understand how society can shed its institutionalized ageism and promote respect for elders.