The chapter begins with a panoramic survey of psychological tests and their often surprising applications. In Topic 1A, The Nature and Uses of Psychological Testing, we summarize the different types and varied applications of modern tests. We also introduce the reader to a host of factors that can influence the soundness of testing such as adherence to standardized procedures, establishment of rapport, and the motivation of the examinee to deceive. In Topic 1B, Ethical and Social Implications of Testing, we further develop the theme that testing is a consequential endeavor. In this topic, we survey professional guidelines that impact testing and review the influence of cultural background on test results.