Criminal contagion is the process whereby the criminality of one person elicits a criminogenic disposition in another. In concert with other factors, criminal contagion contributes to the emergence of a criminal personality rather than to the commission of specific criminal acts. Criminal imitation, on the other hand, presumes an already developed criminal personality that draws from others examples of ideas for concrete ways and means of committing criminal acts. Imitation depends on crime precipitating external factors that contribute to opportunity (time, place, victim, weapon) that must be distinguished from more general criminogenic circumstances. Alcoholics gradually degenerating to some form of property crime because of their addiction illustrate crime-contagious alcohol effects, while violent crimes performed by drunk offenders exemplify situational expressions of already formed criminogenic dispositions. Media influence may have an imitative effect but not a contagious one. Likewise, a rash of suicides using similar means can only be attributed to the imitative effect, which presupposes an already suicidal proclivity. Identifying the origins of imitative criminal acts can be of particular importance to crime investigators, while crime contagion effects have implications for criminality prevention efforts. A total of 59 footnotes are given.