Pitfall traps were used to census ground-active spiders in 12 different habitat types in protected savanna biomes in Tanzania and Namibia. With roughly equivalent trapping effort in the two areas, a total of 229 spider species and 40 families were trapped in Mkomazi Game Reserve and 151 species and 34 families in Etosha National Park. The family composition of the fauna of the two areas was similar, with Salticidae accounting for 17% (Mkomazi) and 14% (Etosha) of all species and Gnaphosidae accounting for 16% (Mkomazi) and 14% (Etosha) of the total. Other families that accounted for a significant proportion of species included Lycosidae (6–7%) and Zodariidae (6–7.5%). Despite the intensive trapping effort, there was no indication from species accumulation curves that a complete estimate of the spider species richness had been obtained from either area. The possible reasons for the differences in spider species richness and family composition in the two areas are discussed. Keywords: Spider biodiversity, family composition, Etosha National Park, Mkomazi Game Reserve.