Abstract: Nuclear magnetic resonance apparatus designed to enable two and three dimensional images of objects to be obtained has coils for applying a static magnetic field and for applying magnetic gradients to the field in each of three orthogonal directions over the entire volume of a sample and a radio frequency signal generator for applying signals having selected frequency components simultaneously with the magnetic field gradients. In use the spins in all regions of a sample except a slice are saturated or excited in the presence of one magnetic field gradient then a slot in the slice is energized in the presence of a second magnetic field gradient and the free induction decay from the slot read out in the presence of a third gradient. The procedure is repeated for successive slots in a slice and for successive slices.