Atlantic and Pacific halibut share many biological characteristics - their reproduction and early life history are nearly identical, and they show the same pattern of age and growth. However, halibut management in the Atlantic and Pacific varies dramatically. Atlantic halibut were managed with other groundfish until 1988; production has ranged from 1000 to 5000 tonnes annually. Pacific halibut has been managed under treaty between the United States and Canada since 1923; production has ranged from 12,000 to 45,000 tonnes annually. Detailed stock assessment of Pacific halibut is described, and extensive biological and fishery data collection is examined.