In otter-trawl catches of Atlantic halibut (Hippoglossus hippoglossusL.) by research vessels from 1959 to 1964, mature males less than 66 to 70 cm long were not regularly encountered. Males were 96 to 100 cm long before the majority were mature, and females slightly longer. The research catches and commercial samples taken by longline from 1961 to 1963 indicated that spawning occurred at various times during the first half of the year. Halibut up to 30 cm long ate invertebrates; from 30 to 80 cm, invertebrates and fish; and over 80 cm, fish almost exclusively.