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The crops in arid and semi-arid regions are often exposed to adverse environmental factors such as high soil salinity. An experiment was conducted in order to determine the response of tomato (Solanum lycopersicum) cv. Microtom to salinity, a variety that has not been extensively studied yet. The investigated elements were the effects on gas exchange parameters, water use efficiency (WUE) as well as leaf area and the contents of total chlorophylls and phenols. At the stage of six leaves, salt stress was applied for 14 days, and three treatments were tested: T1: 0 mM NaCl (Control, irrigated only with rainwater); T2: 50 mM; T3: 150 mM. Sampling events included the collection of tomato leaf samples at two dates: 7 days and 14 days after salt stress application. The obtained results demonstrated that the period of salt stress and salinity treatments had significant effects on the studied parameters, being much more accentuated after two weeks of 150 mM salt treatment. Microtom showed different mechanisms of adaptation to saline stress. Under this stress, the adaptations are mainly morphological (by reducing leaf area), physiological (reduction in net CO2 assimilation rate, stomatal conductance and transpiration, and improvement of WUE) and biochemical responses (decrease of chlorophyll content). Thus, phenol accumulation was stimulated in the leaves of Microtom as a common defensive mechanism. These aspects allowed classifying Microtom as a tolerant cultivar to salinity. (C) 2016 SAAB. Published by Elsevier B.V. All rights reserved.