Analysis of 18 surface sediment samples from between 1 degrees and 64 degrees S, along approx. 180 degrees E, yielded 195 Recent radiolarian taxa. Clustering of the species and the samples, and further examination of the distribution patterns of radiolarian abundances, allowed definition of five climatic zones (tropical to antarctic) and several species groups and isolated species with variable degrees of selective loading on the five areas. Specific diversities were highest in the Tropical Zone, and a secondary peak occurred at the northern edge of the Transition Zone; the latter area was barren of endemic and, probably, also of characteristic taxa. A zonation of the transect, based on a family and suborder level radiolarian census, was similar to the one based on the species, suggesting that the distribution of these higher-level categories is meaningful in ecological terms.