This research was carried out in a non-heated PE tunnel to determine the response of tomato to different EC levels of nutrient solution in closed system comparing with open system during the autumn and spring growing seasons of 2004 and 2005. Tomato (cv. Durinta) plants were grown in perlite culture with a plant density of 3.5 plant m(-2). Plant root volume was 6 liters per plant. The experimental design was factorial randomized parcels with 3 replicates. Plants were fed with a complete nutrient solution at the electrical conductivity levels of (1) 2.0 (control), (2) 4.0 and (3) 6.0 dS/m. Salinity level of the nutrient solution was increased three weeks after planting by NaCl. In closed system, recirculated nutrient solution was replaced after every two unit increase of the EC level for each treatment. Irrigation was based on indoor solar radiation level of 1 MJ/m(2).