Abstract The surface density distribution of manganese nodules in the southern sector of the South Pacific Ocean has been recorded by reference to the complete underwater photographic collection of the U.S.N.S. Eltanin. High concentrations of manganese nodules (75–100% coverage of sea floor) are shown to occur in five main areas: the Southwestern Pacific Basin; the Tasman manganese pavement; the basin centred on 60° S, 100° W; the central region of the Drake Passage; and the crest of the Pacific-Antarctic Ridge (as manganese-encrusted boulders). High surface densities of manganese nodules on the sea floor result from a combination of factors such as low sedimentation rates and high bottom-current velocities. Sea-floor spreading has played an important role in controlling the distribution of massive manganese crusts and manganese nodules across the Pacific-Antarctic Ridge.