Blossom-end rot of tomato fruits occurred when tomato plants (Lycopersicon esculentum Mill. cv. Momotaro) were grown in Ca-rich nutrient solution by using the nutrient film technique. Concentrations of Ca ions were high in both stems and leaves of plants yielding fruits having blossom-end rot. However, Ca concentrations in fruits suffering from blossom-end rot were significantly lower than normal fruits. This indicates that Ca ion diffusion from stems to fruits was physiologically inhibited, resulting in blossom-end rot in fruits. This phenomenon was associated with reduction of photosynthesis. Because plants yielding blossom-end rot absorbed significantly higher concentrations of Mn and Zn ions than healthy plants, it may be possible that enzymes related to calcium transport and photosynthesis might be inhibited with the higher concentrations of heavy metal ions.