Dangerous behaviors refer to acts that are characterized by the application or overt threat of force and are likely to result in injury to other persons. Acts that are commonly defined defined as crimes of violence exemplify the behaviors of major concern; the core offenses of concern to the criminal law are probably represented in the Uniform Crime Reports of the FBI. An individual's dangerousness is considered at many decision points in the criminal justice and mental health systems. A major consideration in efforts to assess, predict, prevent, and change dangerous behavior pertains to the manner in which behavior is conceptualized. Given the vague and overly broad uses of the term 'dangerousness,' it has often been suggested that what should be predicted is the specific dangerous behavior and not some general propensity for violence. Thus, predictions to be made should refer to the probability that certain individuals with particular characteristics, as reflected mainly in past behavior patterns, and functioning in particular social settings, may engage in certain types of behavior, e.g., serious criminal acts, over a given period of time. Predictions must be more systematically and empirically related to probability statements. Public policy concerns involving the prediction of dangerous behavior are mentioned. Three footnotes and 76 references are provided.