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 N – concentration  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 .           Pre – flowering 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 addition to 5.0.0 meq /l. Approximately  plateau trend was found in HAc-Ca content of tomato fruits by increasing Ca in nutrient solution up to the highest level used ( 20.0 meq / l). little increases, but significant ( the least significant differences are 3.4 and 2.44 for the first and second season respectively) in tomato fruit calcium oxalate due to increasing Ca in nutrient solution from 5.0 to 20.0 meq /l . This increase amounted by one tenth, approximately,  of that increase which have been happened in that trait due to Ca level increase of nutrient solution  from 0.0 to 5.0 meq / l . Higher increasing rate was found in HCl – Ca form in tomato fruit due to calcium addition than that of any other form . Calcium silicate of tomato fruit treated with 10.0 meq Ca /l did not significantly differ than that of treated with 5.0 meq Ca/l .   Treatment of 20.0 meq Ca /l significantly decreased these Ca forms compared with that of 5.0 meq Ca /l treatment.                 Post - flowering application of Calcium enhanced N uptake  which in turned N content of tomato fruit in both seasons .  N content of tomato fruit was increased by 3.19 and 3.08 % in the first and second season, respectively . The least significant differences between time application treatment means were 0.05 and 0.06 for the first and second season respectively . So post- flowering Ca application treatment have a higher mean of phosphorus content ( 0.436 and 0.427 %in the first and second season , respectively). Ca application time did not significantly affect potassium content of tomato fruit . Pre – flowering Ca application led to an increase in each of Mg and Na in tomato fruits ( 26.9 and 7.35 %increase in Mg content and Na content , respectively ) . Little change in nitrogen content of tomato fruit as affected by Ca level in nutrient solution was found  in both seasons, where it was ranging between 3.16 to 3.256 % in the first season and between 3.28 to 3.39 % in the second season. post- flowering Ca application at 10.0 meq/l in nutrient solution recorded the highest value in both seasons (3.45 and 3.58 % in the first and second season, respectively).  2.05 and 2.09 % decrease in tomato fruit phosphorus content was found due to nutrient solution Ca increase from 10.0 meqto 20.0 meq /l in the two successive seasons. In both seasons 20.0 meq / l Ca tended to decrease ( 2.44 and 3.69 % decrease in the first and second season, respectively) potassium content of tomato fruit . Mg content of tomato fruit was decreased by Ca addition in nutrient solution, whenever no stedy trend with increasing Ca level in any season was found .  It is worthy to identify that pre- flowering Ca application at 10.0 meq/l recorded the highest Mg content of tomato fruit ( 528 and 538 ppm for the first and second season , respectively ) The lowest values of sodium content of tomato fruit were found at 0.0 Ca level in both seasons . The highest values in both seasons ( 178 ppm for the first season and 173 ppm for the second one ) were obtained due to 5.0 meq Ca /l treatment . 10.0 and 20.0 meq Ca /l treatment means of sodium content  were lower than that of 5.0 meq Ca /l treatment by 17.42 and 28.65 %in the first season, corresponding values in the second season were 17.63 and 28.90 %