Root growth of barley (Hordeum vulgare L., cv. Akashinriki) was inhibited by 200 mM NaCl, when 1 mM CaCl2 was present in the hydroponic culture solution. Increasing the CaCl2 up to 10 mM partially prevented this inhibition. However, inhibition also occurred with 100 mM NaCl in the presence of 0.1 mM CaCl2. The nuclei of meristematic cells in roots in which growth had been inhibited by salt stress were studied after staining with DAPI (4',6-diamino-2-phenylindol). Nuclear deformation of the cells occurred with 12 h of salt stress with 500 mM NaCl, and was followed by degradation. The nuclear degradation was also observed when the roots were exposed to more than 300 mM NaCl for 24 h. Biochemical analysis revealed that nuclear degradation was accompanied by apoptosis-like DNA fragmentation, The intracellular mechanisms of nuclear degradation in cells after salt stress are discussed.