Two field experiments were carried out under saline condition at Wadi Sudr, Agricultural Experimental Station, South Sinai Governorate during 1997 and 1998 seasons to evaluate the salt resistance of tow tomato cultivars (Edkawy and Castle Rock) . Furthermore, the possibility of increasing their salt resistance by application thidiazuron (TDZ) at 0.5, 1.0 ppb and/or KCl at 1.0 and 2.0 % were studied under saline condition. Generally, Castle Rock cultivars exhibited a vigorous growth characters, yield and yield components than those of Edkawy. Application of TDZ and/or KCl at any level significantly increased all growth parameters, yield and yield components of both cultivars as compared with the control. The best results of growth and yield were obtained by combination TDZ at 1.0 ppb with KCl at 2% either in Castle Rock or Edkawy cultivars. As for chemical composition in tomato shoot, i.e. K, Na, Ca, Mg and K/Na ratio, Castle Rock cv. had the lowest contents of Na and the highest contents of K, Mg, Ca, and K/Na ratio as compared with Edkawy cultivar. TDZ application significantly decreased Na contents in both cultivars, whereas, K/Na ratio reached the highest value. Combined TDZ at 0.5 ppb with KCl at 1% gave the best result to decrease Na content in Castle Rock and Edkawy cultivars. However, its combination increased K/Na ratio that reached three fold in Castle Rock comparing with Edkawy cultivar. In this respect, additional KCl at 1.0 &2.0% could positively affect K/Na ratio in Edkawy cultivar, meanwhile, such ratio in Castle Rock cv.  was not affected. The role of bioregulator (TDZ) or KCl for increasing salt resistance via altering K/Na ratio was discussed. Also, the effect of previous treatments on tomato yield was recorded.