subtilis in ratios of 9(GAT):1(GKS) down to 6(GAT) :4(GKS) after which additivity, indifference and antagonism, in that order, were manifested as the ratio of GKS increased in the combination. Against S. aureus, the combined interaction showed a somewhat irregular pattern of effect, including synergism at GAT:GKS ratios of 9:1, 2:8 and 1:9 , antagonism at ratios of 8:2, 5:5 and 4:6 and indifference at GAT:GKS ratios of 7:3, 6:4 and 3:7. Conclusion:The results from this study suggest that the effect of combination of the methanol extract of GKS with gatifloxacin was dependent not only on the ratio of combination but also on the test organism employed for the evaluation. Overall, the combined antimicrobial effect of the interaction between GKS and gatifloxacin was predominantly synergistic against B.subtilis.