The contents of K + , Mg2+, Na+, Ca2+, Rb+, Mn2+, Cu2+, Al3+, P, Br“, and CL were measured in tomato fruits, which were picked from the plant at various stages of development, starting from the day of anthesis. Determinations were also carried out of transpiration rate, increase in fruit water, and dry and combustable fruit materials. Measurements of the ion contents in the fruit, and the import characteristics of Ca2+ indicated that the ratio of C02 production and photosynthetic COj fixation rates did not appreciably change during the entire period of fruit growth. The overall efficiency of conversion of imported to fruit dry matter was assumed to be about 100%. The high initial ion concentrations in the fruit have been attributed to an initially high rate of water and solutes supply by the xylem. The varying fractional contribution of the xylem to ion and water import results in varying import rates of solutes in the fruit. The maximal percentage of phloem delivery during the period of highest growth rate could be estimated as 99, 98, 94, 0, 99, 78, 93, 94, 98, 97 and 97% for K+, Mg2-1-, Na+, Ca2+, Rb+, Mn2+, Cu2+, Al3+, P, BL, and CL respectively. The average fractional phloem contribution to the import of dry matter and water could be determined as 98 and 84% respectively. The amounts of Ca2+, imported during the early stages of fruit development, were shown to be important with respect to the avoidance of the occurrence of blossom-end rot during the period of highest growth rate of the fruit.