Aims: To evaluate antimicrobial and cytotoxicity activities of Clausena anisata, Acokanthera shemperii and Olea europaea against seven Gram negative bacteria and fungal species. Study Design: Bioassay of antimicrobial assay was done using 96-well micro-dilution method. Place and Duration of Study: School of Life Science and Bioengineering, Nelson Mandela African Institution of Science and Technology, Arusha, Tanzania, from April 2014 to June 2014. Methodology: 96-well micro dilution method was used in antimicrobial assay. Extracts were loaded in the wells of the first row, followed by serial dilution and 50 μl of the bacterial suspensions (0.5 MacFarland standard turbidity) were added in each well. The first concentration which showed no bacterial growth was considered as minimum inhibition concentration. Method developed by Meyer et al 1982 was adopted in cytotoxicity activities. Results: All extracts indicated antibacterial activity on at least three to five of the tested seven bacteria and two fungi species with MIC value ranging 0.7812 - 12.5 mg/mL. The highest activity