ABSTRACT Pubescent Chionoecetes bairdi females were held in isolation and placed with males at selected times during a 70-day period following their molt to maturity. Some primiparous crabs that mated within 27 days of their molt produced viable clutches, while others produced externally attached nonfertilized eggs during the isolation period. The fertile period for primiparous C. bairdi varied with the individual, and ranged from less than 1 to 28 days. Multiparous females either utilized sperm stored in their spermathecae from a previous mating to fertilize new eggs, or mated prior to egg extrusion. Those multiparous crabs that were allowed to mate within four days after cleaning their pleopods produced viable egg clutches, but by day seven some females did not attract males or breed. These observations suggest that the period in which individual multiparous C. bairdi are receptive to breeding ranges from less than one to seven days.