The diatom flora in two series of samples collected, one in 1961/2 and the other in 1983, from the thermal spring complex at Gross Barmen near Okahandja in South West Africa/Namibia are documented. Taxonomic notes are provided for most of the 63 taxa recorded, and each taxon confirmed as present is illustrated with light microscope photographs. One new species, Navicula pseudosydowii sp. nov., and one new variety, Anomoeoneis sphaerophora var. magnifica var. nov., are described. The structure of the diatom assemblages in the two series of samples is discussed briefly, and comments are made on the influence of temperature on the distribution of species in thermal waters. Keywords: Anomoeoneis sphaerophora var. magnifica var. nov, Bacillariophyceae, diatom assemblages, Navicula pseudosydowii sp. nov.