Social organization of Roosevelt elk (Cervus canadensis roosevelti) and its interrelationship to habitat use was studied at Prairie Creek Redwoods State Park, California. Behavior and movements were observed in the Gold Bluffs Beach herd, whose size ranged between two and 27 and averaged 16 members. This matriarchal herd was a semistable association in which elk entered and left the group freely. The adult females and their calves formed the most constant part of the herd. Other sex and age classes were less attached to this cow-calf nucleus. Older cows usually dominated younger ones. Cow herd composition was most stable for the seven months from November through May. Division of the cow herd into smaller units was high during calving, post-calving, and rutting periods. As males increased in age from yearlings to adults, they left the herd and joined groups of males. Males associated with the cow herd more often in winter than during other seasons. The size of groups of elk was largest on the prairies, smallest in the brushland, and most variable in cutover redwood forest. The home range was a 9.6-kilometer long and 100 to 450-meter wide strip of beach and coastal prairie with a surface area of three square kilometers. Use of the home range's three ecological regions was highly correlated with available forage (r = .98). The herd spent over half its time within the central fourth of its home range, an area with a relative abundance of preferred herbaceous perennial forage. Although no active defense was observed, the central area was exclusively occupied by the tagged study herd and no other groups of elk were ever seen there.