The cannabinoids produce a variety of effects on unlearned behavior in different animal species. The voluminous literature pertaining to cannabis and unlearned behavior has been reviewed in the five previous Marihuana and Health Reports (1971 through 1975). The present chapter relies heavily on these previous reports for background and focuses primarily on the relevant literature which has appeared during the past two years, although a continuing attempt is made to consider the more recent literature in the context of previous findings. As in the 1975 Marihuana and Health Report, the present chapter is organized for expository purposes around four categories of unlearned behavior: gross behavior; activity and exploration; consummatory behavior; and aggressive behavior.