Nineteen locally selected potato lines were screened for water stress tolerance by measuring the growth parameters in vitro. The stress was achieved by adding 4% of sorbitol to the growth medium. Plant height and diameter, leaf area, number, length and diameter of roots and plant fresh and dry weight were measured. The results showed a difference in the response of the studied lines to water stress, cluster analysis, based on the sum of all growth parameters relative values of the lines showed that the lines were divided into three groups according to water stress tolerance: The tolerant group, the moderate tolerant group and the sensitive group. The results indicated the possibility to use the in vitro method to screen the potato lines for water stress tolerance.