Background Volatile anaesthetic agents influence neutrophil function, and potentially, the inflammatory response to surgery.Aim The objective of this study was to determine the effect of isoflurane (1-4%) on human polymorphonuclear neutrophil apoptosis in vitro.Methods Venous blood from 12 healthy volunteers was exposed to 0, 1, and 4% isoflurane delivered via a 14G Wallace flexihub internal jugular cannula, at a fresh gas flow of 0.5l/min for 5 minutes. Isolated neutrophils were assessed for apoptosis at 1, 12, and 24 hours in culture using dual staining with annexin V-FITC and propidium iodide (Annexin-V FITC assay). Data were analysed using paired, one-tailed Student's t-tests. p <0.05 was considered significant.Results At 1 hour apoptosis was inhibited in the 1% (5.1 [6.8]%; p=0.017) and 4% (4.8 [4.5]%; p=0.008) isoflurane groups compared to control (11.3 [6.9]%). At 12 and 24 hours, a dose-dependent inhibition of apoptosis was demonstrated, i.e. 4% > 1% > 0%.Conclusion Human neutrophil apoptosis is inhibited in a concentration-dependent manner in vitro by isoflurane in clinical concentrations.