S U MM ARY Feline spinal cords were traumatised by the weight dropping technique. Five trauma groups were studied (5 gX80 cm, 10 gX40 cm, 20 gX20 cm, 40 gXl0 cm, and 80 gX 5 cm), each having a 'standardised' injury of '400 g-cm.' The spinal cords were sectioned serially two hours after contusion and examined by light microscopy. Relative to the larger weights falling from lesser heights, the smaller weights falling from greater heights were associated with less haemorrhage, oedema, axonal disruption, and myelin fragmentation as well as a smaller volume of grey matter containing altered anterior horn cells. In all trauma groups the cortical evoked responses disappeared at the time of the injury and did not reappear. Even though each trauma group received a '400 g-cm' contusion, each weight-height combination was associated with differing degrees of histopathological alterations. A plea is made for more accurate quantitation of experimental spinal cord trauma than the 'g-cm' unit.