The mating behavior of the crayfish, Procambarus clarkii, was studies bycomparative behavior experiments. The mating process of the crayfish was divided intopremating phase and mating phase which included 5 events: (1)capturing; (2)turning; (3)crossing; (4) copulating; (5) disengaging. The behavior experiments revealed that thefemales displayed submitting behavior after being grasped by the males,but never after beinggrasped by same sex. The males showed premating behavior when closed to the females, butbecame rather aggressive when closed to the same sex. The crossing leg of the male inmating was confined to the right peraeopod. Whether a mating proceeds sucessfullydepended on how the male approached the female. The mean number of copulations perindividual was significantly greater for larger males than for smaller males.