Salinity is one of the main restricting factors for crop production in the arid and semi-arid regions of the world. An experiment was conducted in research center culture without soil at Isfahan University of Technology, Isfahan, Iran (40 0 85 / N, 77 0 83 / W) during March and May 2011, in oder to evalute the response of linseed ( Linum usitatissimum ) genotypes to different levels of salinity. The pot experiment was laid out usinig a factorial arrangement in a randomized complete design with four replications. In this experiment, four linseed genotypes (Kordestan, Flandrez, Makgeregur, AC 1 ) were tested at four salinity levels (0, 30, 60 and 90 mM of NaCl). Plant hieght, number of leaves per plant, leaf area per plant, plant dry weight, the concentration of sodium and potasium in shoot and root, chlorophyll and prolin content and lipid peroxidation rate of plant were measured. Salinity deacresed plant height, number of leaves per plant, leaf area per plant, shoot and root dry wieght, the concentration of potasium in shoot and root and leaf chlorophyll contents but the proline content, lipid peroxidation rate, sodium concentration in shoot and root and sodium/potasium concentration ratio were increased under saline condition. There were significant diffrences among linseed genotypes in terms of plant height, laef area per plant and root and shoot dry weight, proline and chlorophyll contents, lipid peroxidation rate and sodium and potasium concentrations in the roots. The interaction between salinity levels and cultivars was significant for plant height, plant dry weight, leaf area per plant, chlorophyll a content and proline content but it was not significant for number of leaves per plant, shoot and root dry wieght, shoot/root dry wieght ratio, sodium and potasium concentration in shoot and root, total and b chlorophyll content and the lipid peroxidation rate. The extent of reduction in plant dry weight under saline treatments were not similar for the tested genotypes.The most (63%) and the least (46%) reduction in plant dry wieght were belong to AC 1 genotype and Kordestan, respectively. The highest amont of plant dry weight was achived for Kordestan under unsaline condition and the lowest amount was belong to AC 1 genotype at 90 Mm of NaCl. The tolerant genotype (kordestan) acumulated more proline in the leaves under salin condition comparted to more sensitive genotype.The result of this experiment showed that salinity can significantly affect the growth of linseed genotypes and the response of the evaluted genotypes to salinity were different. Key Words : linseed, salinity, genotypes, ionic content, proline, lipid peroxidation rate