MANY investigations of bacterial metabolism require that the contents of the cell be released. This apparently simple requirement has not yet been met in a completely satisfactory way. The present method differs in principle from previous techniques. It consists of sudden release of applied gas pressure and is very simple, rapid and inexpensive. Under optimum conditions, bursting of well over 90 per cent of the cells is easily attained, and the only substance introduced is a gas which has been shown to be non-injurious to the bacteria.