The study was conducted to assess the antibacterial activity of <i>Phyllanthus</i><i> </i><i>amarus</i><i> (</i>Schum and Thonn) extract against <i>Salmonella </i><i>typhi</i> causative agent of typhoid fever at the laboratories of the Departments of Chemistry and Theoretical and Applied Biology of the College of Science, Kwame Nkrumah University of Science and Technology, Kumasi. The objectives were to determine the highest yield of crude extract of <i>P. </i><i>amarus</i><i> </i>using different proportions of water to ethanol and to determine the sensitivity of <i>Salmonella </i><i>typhi</i> to these. Three different extraction procedures were carried out. In the first procedure, seven extraction setups each containing different proportions of the two extract (water and ethanol) were used with 10g of the plant sample. In the second procedure, eight setups were used for the two solvents. Ten grams of both fresh and dry plant sample were extracted in two different 200ml of water and in another two different 200ml of water; 20g of both fresh and dry plant sample were again extracted. The same procedure was repeated using ethanol as the solvent. In the third procedure, 10g each of fresh plant sample were boiled in 100ml and 200ml of water for 30 minutes. A sensitivity test to determine the zones of inhibition for the various plant extracts was done on <i>Salmonella </i><i>typhi</i> isolated from human. Results from the crude yield of <i>P. </i><i>amarus</i> using water only had the highest crude yield of 2.57g, followed by ethanol only which was 2.52g. The sensitivity studies conducted on the fresh <i>P. </i><i>amarus</i><i> </i>indicated that aqueous extract of <i>P. </i><i>amarus</i><i> </i>inhibited <i>S. </i><i>typhi</i> to a zone of 5.00mm in 10g/200ml and 7.17mm in 20g/200ml. Ethanol extract also recorded an inhibition zone of 2.67mm and 5.33mm in 10g/200ml and 20g/200ml respectively. Again, sensitivity studies using dry <i>P. </i><i>amarus</i><i> </i>samples showed that the aqueous extracts recorded a zone of inhibition of 7.33mm in 10g/200ml and 13.50mm in 20g/200ml. Also ethanol extracts also recorded an inhibition zone of 6.83mm in 10g/200ml and 10.50mm in 20g/200ml. Significant differences were observed among the extracts and the control in both 10g/200ml and 20g/200ml concentrations (P<0.05). Aqueous and ethanol extracts of <i>P. </i><i>amarus</i><i> </i>proved inhibitory to <i>S. </i><i>typhi</i>.
