Research on people's accuracy in perceiving other people's states, traits, and social attributes has existed for over 100 years. In the past few decades, however, it has exploded into a vibrant, interdisciplinary, and international pursuit with relevance to all areas of social, interpersonal, and intrapersonal life. However, researchers typically work within narrowly defined traditions within the field. The present volume brings these areas together to describe method, theory, and findings for seven content domains (judging emotions, thoughts and feelings, truth versus lie, personality, social attributes, others’ views of self, and group attitudes). Correlates at the group, individual, and situational levels are discussed, as well as the basic question: how accurate are people in judging other people? The strengths, weaknesses, and gaps in this field are discussed, and directions for future research are offered.