Abstract: There is described a method and apparatus for measuring the volume of an object by means of penetrating radiation. The object is placed in an irradiation zone and measurements of amounts of radiation passing through respective areas of the object are made. From each measurement, a value representative of the “thickness” of the object at that area is derived, and by adding the representative values, a “volume” is calculated. The object is preferably moved through the irradiation zone, while radiation is measured by means of a linear array of sensors extending perpendicularly to the movement direction.