Ethanolic extracts of 20 selected plant species used by Yemeni traditional healers to treat infectious diseases were screened for their antibacterial activity against both Gram-positive and Gram-negative bacteria, as well as for cytotoxic activity. Fourteen of the ethanolic extracts showed variable degrees of antibacterial activity. The active ethanolic extracts were partitioned between ethyl acetate and water for a first separation. The ethyl acetate extract of Lawsonia inermis was found to be the most active one against all bacteria in the test system. Other promising results could be obtained from extracts of Aloe perryi, Indigofera oblongifolia, Meriandra benghalensis and Ziziphus spina christi. Additionally, the ethanolic extracts of the 20 plants under investigation were tested for their cytotoxic effects on FL-cells using the neutral red assay. Extracts of Calotropis procera, Chenopodium murale, Pulicaria orientalis, Tribulus terrestris and Withania somniferum displayed a remarkable activity.