The distribution of benthic Ostracoda on the continental shelf and upper slope between Cape Agulhas and the Kunene River is shown to be related to various time-averaged oceanographical and sedimentary parameters. The microfossils represent mixed modern and relict assemblages, probably dating from Recent to late Holocene time (c. 7000 yr B.P.). For each of the 36 most abundant species ( gt 95% of the total ostracod assemblage, with 123 species) mean values for a range of environmental sea-floor parameters have been calculated. These relate to water properties (temperature, salinity, dissolved oxygen) and substrate characteristics (sand, mud, calcium carbonate, total organic matter, elemental Fe and authigenic mineral contents). Correlation coefficients between these parameters and individual species indicate which parameters are the most important in determining distributions. On a regional scale, the various areas of the continental shelf are dominated by a particular species. North of about 24 degree S, upwelling-induced low dissolved oxygen and high total organic matter (MORG) values favour Cytherella namibensis (outer shelf) and Palmoconcha walvisbaiensis (inner to mid-shelf), respectively. Farther south, the influence of advected, well-oxygenated Antarctic Intermediate Water on to the uppermost slope and outer shelf controls the distribution of Ruggieria cytheropteroides, whereas on the mid- and inner shelf, variations in mud and terrigenous components are the main controls for Pseudokeijella lepralioides and Bensonia knysnaensis dnysnaensis, respectively. In water deeper than about 500 m, the dominant species along the whole margin is Henryhowella melobesioides, whose distribution is primarily controlled by temperature/salinity variations. (Closer inshore, mud content of bottom sediments is more important.) For the other most abundant species, the main environmental controls are substrate-dominated, with sand and calcium carbonate (mainly negative) the most important. Elemental Fe (which is used as a gauge of the terrigenous component) is also important (both positively and negatively), with total organic matter more frequently important than any of the bottom-water properties. Barren areas (sparse or no ostracod faunas) occur in both shallow and deep water, and are associated with the effects of upwelling (north of 27 degree S), fluvial terrigenous input (Namaqualand inshore area), and isolation from sources of terrigenous and organic matter (either side of the Cape Canyon).