Four cultivars (Blitz, Mariachi, Quest and Rapsodie) of tomato were grown hydroponically on rockwool in two microclimates (east and west) inside the greenhouse (Tucson, AZ) under two nutrient solution electrical conductivity (EC) levels (2.6 or 4.5 dS m-1), adjusted by adding NaCl and CaCl2 after the setting of first fruit truss. In all cultivars, total soluble solid (TSS, %Brix at 20oC) and lycopene concentration of fruits increased by 12-23 % and 34-85 %, respectively, with increasing EC level. Fruits harvested from the east side of the greenhouse had higher TSS than those from the west side, due to the different plant microclimate varying by daily PPF (photosynthetic photon flux) and VPD (vapor pressure deficit). However, lycopene concentration in fruits was not significantly affected by plant microclimate regardless of cultivars or EC. The cultivar Mariachi had the strongest effect in response to nutrient solution EC levels regarding both TSS and lycopene concentration among the cultivars examined. The cumulative yield at 7 weeks had no significant differences between nutrient solution EC and locations, regardless of cultivars. The results indicated that value added tomato fruits could be produced by manipulating EC and plant microclimate in the greenhouse without causing yield reduction.