||This paper had as principal objective identification of potato varieties with tolerance to water stress by using “in vitro” tissue culture and mannitol, in different concentration, as an agent to induce water stress simulation. Mannitol added to the culture nutritive medium had five levels (0.36, 0.73, 1.11, 1.46, 1.92%). The starting point was represented by plantlets culture collection, belonging to Romanian varieties: Rustic, Tampa, Ruxandra, Robusta, Gared. Plantlets were multiplied between two internodes to obtain microcuttings (in sterile condition), which were inoculated on medium established by Murashighe & Skoog (1962), enriched with vitamins to which is added sucrose, agar, growth regulators (for control media). There were other variants of media, to which was added at each mannitol concentrations. After 4 weeks was made the determination of values for different morphological parameters (plantlets height, number of leaves / plantlet and fresh weight of plantlets) – which were statistically analyzed by Duncan test. Water stress affected plantlets length, number of leaves and plantlets fresh weight. The varieties showed different responses. Plantlets height decreased dramatically by exposure to high concentrations of mannitol. This is due to a possible mechanism of water stress intolerance. “In vitro” simulation of water stress for Romanian potato varieties, under the influence of a high osmotic potential, may provide an efficient system of differentiation for varieties tolerant to drought, under field conditions.