Processes of heat and mass exchange that take place in the course of wheat grain wetting and drying, cause inner stress resulting in endosperm cracks. These cracks cause specific physical and biological effects. Spring wheat grain, cv. Henika, with an initial moisture content of 10% and varied endosperm structure (mealy and vitreous), was wetted for 1, 3, 6 and 9 h and then dried in room conditions to initial moisture content. Inner cracks to grain caused by the processes mentioned above, were detected by means of soft X-ray technique. The physical endosperm condition was described by the number of cracks. Barrelshaped core samples, cut from some selected kernels, were then subjected to uniaxial compression tests to determine such parameters as: compressive strength (smax), modulus of elasticity (E), strain (emax) and specific work (wmax). A significant, high, negative correlation was found between grain mechanical properties and their earlier wetting time. Similarly high and significant correlation was noted between these properties and the number of inner cracks. Vitreous kernels were characterized by higher values of mechanical properties than the mealy ones.