A greenhouse experiment was conducted at Fac. of Agric., Mansoura University during the two summer successive seasons of 2010 and 2011 aimed to investigate the effect of Ca concentration ( 0.0, 5.0, 10.0 and 20.0 meq / l) in nutrient solution and its application time (pre flowering and post flowering) on tomato fruit composition. Combination between the studied factors levels comprise eight treatments which were arranged in a split block design with 3 replicates . All treatments were studied in the presence of Nconcentration at rate of 150 ppm . The obtained results can be summarized in the following :-Total calcium content of tomato fruit was increased by 19.64 % in the first season and 6.06 % in the second season as a result of post-flowering application of calcium .Relatively higher increases were found in Etha-Ca ( 8.01 % ) and H2O-Ca ( 7.99 % ) in the first season compared with that of the second season ( 1.87 for Etha-Ca , 1.93 for H2O-Ca) due to pre flowering Ca application .Preflowering calcium application reduced Na Cl-Ca (6.82 and 5.94%) ,HAC-Ca (6.38 and 11.54 %) and HCl-Ca (3.19 and 9.34 %) in tomato fruits in both seasons.Increasing calcium levels up to 10.0 meq /l significantly increased total calcium of tomato fruits, while rising calcium level from 10.0 to 20.0 meq /l significantly decreased total calcium content of tomato fruitsin the first season . In the second season, increasing calcium levels up to 10.0 meq /l increased total calcium of tomato fruits but the difference in that trait between treatments of 5.0 and 10.0 meq /l is not detectable . So calcium level of 20.0 meq /l reduced total calcium content by 9.21 % compared with treatment of 10.0 meq /l in the second season .Post-flowering application of Ca at a rate of 5.0 meq/l have the highest value of total Ca in tomato fruits( 4446.9 and 3895.5 ppm in the first and second seasons).Appling 5.0 meq / l treatment achieved the highest values of Eth-Ca in both seasons ( 155.2 and 169.4 ppm for the firs and second season , respectively ). Increasing Ca level above 5.0 meq /l significantly decreasd Eth -Ca in bothseason in tomato fruits .In spite of increasing H2O -Ca form significantly by adding 5.0 meq / l than that of control (60.0 and 65.455 increase in the first and second season ) . Significantly decrease ( comparing to 5.0 meq / l treatment ) with increasing Ca level behind that was found .NaCl -Ca in tomato fruits refer to Ca in pectate form which caused fruit hardness have a strongly increasing trend by increasing Ca level in nutrient solution from 0.0 Ca addition to 5.0 meq /l in nutrient solution) .Na Cl -Ca represent the large portion of Ca in tomato fruit . Post-flowering application of 5.0 meq Ca/l maximize of NaCl-Ca , where 3440 and 2884 ppm Ca were found in this form in the first and second season, respectively . HAC-Ca {Calcium phosphate and Calcium carbonate} in tomato fruits have a strongly increasing trend by increasing Ca level in nutrient solution from 0.0 Ca

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