My invention relates to a method for sterilizing or pasteurizing container-packed products such as plastic bags (pouches) while using a conveyor with box-shaped carriers, jointly covering a path in a space, provided with nozzles for supplying a liquid heated to the desired temperature. Such a method is known, for bottles, from the French Pat. No. 619,254. This publication relates to a so-called beer pasteurizer in which the product to be treated needs only be exposed to a temperature below 100.degree., so that a treatment space can be used which freely communicates with the ambient atmosphere.