The antimicrobial activity of five samples of Taxandria fragrans essential oil was evaluated against a range of Gram-positive (n= 26) and Gram-negative bacteria (n= 39) and yeasts (n= 10). The majority of organisms were inhibited and/or killed at concentrations ranging from 0.06-4.0% v/v. Geometric means of MIC were lowest for oil Z (0.77% v/v), followed by oils X (0.86%), C (1.12%), A (1.23%) and B (1.24%). Despite differences in susceptibility data between oils, oils A and X did not differ when tested at 2% v/v in a time kill assay against Staphylococcus aureus. Cytotoxicity assays using peripheral blood mononuclear cells demonstrated that T. fragrans oil was cytotoxic at 0.004% v/v but not at 0.002%. Exposure to one or more of the oils at concentrations of <or=0.002% v/v resulted in a dose responsive reduction in the production of proinflammatory cytokines IL-6 and TNF-alpha, regulatory cytokine IL-10, Th1 cytokine IFN-gamma and Th2 cytokines IL-5 and IL-13 by PHA stimulated mononuclear cells. Oil B inhibited the production of all cytokines except IL-10, oil X inhibited TNF-alpha, IL-6 and IL-10, oil A inhibited TNF-alpha and IL-6, oil C inhibited IL-5 and IL-6 and oil Z inhibited IL-13 only. IL-6 production was significantly inhibited by the most oils (A, B, C and X), followed by TNF-alpha (oils A, B and X). In conclusion, T. fragrans oil showed both antimicrobial and anti-inflammatory activity in vitro, however, the clinical relevance of this remains to be determined.