In this studywe estimate the biomass and describe the distribution of the two main jellyfishpopulations (Chrysaora hysoscella and Aequorea aequorea) encounteredin the northern Benguela system off Namibia. Findings are based on datacollected with BONGO nets, towed in the upper 50 m during eighteen ichthyoplankton surveys over the period 1982-1989. The results gave an averagewet biomass of about 10.8 million tons Aequorea (mean density 66 g m^-2) and 29,7 million tons Chrysaora (mean density 181 g m^-2). The largest jellyfish concentrations were encountered between 18º and 26º30’ S(north of the Lüderitz upwelling cell), and more than 90% of their totalbiomass occurred within 45 nautical miles of the coast. Longshore and offshoredistributions of Aequorea and small and large Chrysaora arecompared. Temperature preferences were derived from the same data series andfrom a review of changes in distribution patterns of both species during apronounced Benguela Niño event in 1984. The suspected predatory impact of thesejellyfish on larval fish stocks is discussed in conclusion.