Attention has been drawn to the possible deliterious effects on operating theatre personnel of breathing in an atmosphere polluted with anaesthetic vapour, in particular, halothane. Whether or not the relation of these effects of anaesthetic vapours has been adequately proved, there is unlikely to be any disagreement that pollution of theatre air with anaesthetic is undesirable. Comparable atmospheric pollution with halothane in the same theatre was studied with and without use of halothane absorber "Aldasorber". The theatre had no device for reducing air pollution. Anaesthetic exhaust fases were drained to the ground. An anaesthetic machine in a semiclosed circle with carbon dioxide absorber was used throughout the anaesthesia. Anaesthesia was maintained with halothane l.0% and 50% oxygen in nitrous oxide, free gas flow rate were oxygen l.5 liter/min and nitrous oxide 1.5 liter/min, Halothane concentrations at various sites of the operating theatre were studied using the method of gas chromatography. 1) Halothane concentrations in the atmosphere of the operating theatre were 0.11 ±0.07 ppm without halothane absorber and 0.13 ±0.14 ppm with halothane absorber at the level of 115cm above the operating theatre floor before anaesthesia. 2) Halothane concentrations in the atmosphere of the operating theatre were 7.50 ±1.32ppm without halothane absorber and 2.82 ±0.93 ppm with halothsne absorber at the level of 115cm above the operating theatre floor after 3 hours of anesthesia. 3) Comparing this data it was concluded that the concentration of halothane vapour in the operating theatre air after 3 hours of anesthesis could be reduced by 65% W1th halothane absorber Aldasorber.