Cracking in two varieties of potatoes was investigated by compressing whole tubers between flat plates at low compression rates. It was found that resulting crack areas correlated directly with the energy stored at cracking. Of the energy imparted to the tuber, a large proportion is dissipated during compression.Cracking occurs when the stored energy exceeds a critical value, approximately 1.6 J for Sebago and 0.9 J for Pontiac. The extent of cracking is determined by the fracture toughness, calculated to be 1350 Jm−2for Sebago and 1230 Jm−2for Pontiac. The Sebago variety is thus more resistant to cracking than Pontiac. The energy dissipative mechanisms in hysteresis and crack propagation are explained in terms of the structure of potato tis