Six crab species inhabit the rocky intertidal of the South Island of New Zealand: Petrolisthes elongatus, Heterozius rotundifrons, Hemigrapsus edwardsi, H. crenulatus, Cyclograpsus lavauxi and Helice crassa. The grapsid C. lavauxi is the most abundant and ubiquitous species: its intertidal distribution was uniform between sites - the lower limit (within approximately 5 cm of MSL) and the upper limit (150 cm above MSL) being determined by the availability of suitable rocky substrate or aerial exposure. Highest densities were on sheltered rocky beaches on the open coast line. Another grapsid H. edwardsi, the major potential competitor, overlapped with C. lavauxi between 0 and 100 cm above MSL. Gut content analysis suggested that both species feed almost exclusively on the same brown algae. Tide tank experiments suggested that the zonation of both species is primarily associated with tidal exposure times. At field sites where H. edwardsi was absent, the lower limit of C. lavauxi was unchanged. Our results support the hypothesis that interspecific interactions are of little, if any, importance in determining intertidal distribution of these grapsid crabs.