High pressures and anaesthetics were used to study chilling injury in plants. Changes in membrane fluidity at low but nonfreezing temperatures are thought to be involved in chilling injury-a physiological disorder of many economically important plants, e.g. banana, cotton, cucumber, maize, rice, sorghum, and tomato. High-pressure helium and nitrogen atmospheres of 12 MPa increased the severity of chilling injury (i.e. rate of ion leakage) in excised cucumber cotyledon discs, cucumber hypocotyl segments and tomato pericarp discs, and also increased the threshold temperature at which chilling occurred by 2° to 6°C. Exposure to vapours of the anaesthetics halothane and methoxyflurane reduced chilling injury in cucumber cotyledon discs, cucumber hypocotyl segments and tomato pericarp discs. The relative effectiveness of the two anaesthetics in reducing chilling injury was similar to their relative effectiveness in inducing anaesthesia in animals and their relative lipid solubilities. The response of the tissues to halothane and methoxyflurane, which increase membrane fluidity, and to high pressures, which reduce membrane fluidity, are consistent with the hypothesis that cold-induced phase transition of membranes could be responsible for chilling injury. However, other cellular components may also be affected, e.g. low temperatures, high pressures and anaesthetics can alter protein conformation, affect ion channels, depolymerize microtubules and cause the release of calcium from membrane lipids.