Forty-three different plant species commonly used in traditional medicine for the treatment of malaria were selected and screened for their antimalarial activity against Plasmodium falciparum in vitro. Thirteen of the 43 species were obtained directly from traditional healers who use these plants for the treatment of malaria. The other plant species were collected on the basis of ethnomedicinal information in the literature. The plant material was collected from Morogoro, Dar es Salaam and Kagera regions in Tanzania. Fifty-eight plant samples from these 43 plant species, including leaves, roots and stem bark, were investigated. Apart from the crude EtOH extracts, petroleum ether (PE), ethyl acetate (EtAc) and H2O fractions of these extracts were also tested. The in vitro testing revealed that 37% of the investigated plants showed strong antimalarial activity with IC50 values below 10 micrograms/ml. The four most active plants included Cissampelos mucronata, Maytenus senegalensis, Salacia madagascariensis and Zanthoxylum chalybeum.