Social influence occurs when behavior by one person causes another person to change an opinion or to perform an action he or she would not otherwise perform. This chapter discusses influence based on legitimate authority. It considers some interesting experimental studies of destructive obedience. These studies illustrate the extremes to which authorities can push behavior. The chapter considers some factors that determine whether a target will comply or refuse to comply with an authority's directives. It examines the threats and promises in more detail. Threats and promises are influence techniques used to achieve compliance from the target. The chapter also discusses three major contributors to persuasion resistance: inoculation, forewarning, and reactance. It also discusses how the characteristics of the source and the content of the message affect persuasion. The communication-persuasion paradigm points to many factors—properties of the source, the message, and the target—that affect whether a message will change beliefs and attitudes.