In VITRO grown potato cultivars shoots were used to understand ….. how polyvinyl pyrrolidone (PVP) and three levels of potassium interact with two levels of salinity to determine Na+ and K+ contents, and antioxidant enzyme activities leading to control survival, multiplication and growth of cultured plant shoots. Explant survival and number of regenerants/explant decreased with increase of NaCl concentration but increased K+ content of the culture medium from 20 mM to 30 mM improved explants survival frequency and the growth parameters estimated under relatively high salt stress (80 mM NaCl) in both cultivars. Also, number of regenerants was influenced by K+ level where it was higher on medium containing 40 mM NaCl and 30 mM K+ than other cultured on the same NaCl concentration with 20 mM K+. The positive effect of 30 mM K+ on the previous parameters was associated with increase shoot K+ content leading to decrease Na+/K+ ratio and increase of some antioxidant enzymes (SOD, POX and CAT in Agria or SOD, POX and APX in Hermes) activity, especially under relatively high salt stress. PVP application increased K+ content and activities of some antioxidant enzymes (CAT and APX) but decreased Na+/K+ ratio of shoots subjected to relatively high salt stress in Agria but under both salt stresses in Hermes. Consequently, sufficient potassium supply was necessary to conserve low Na+/K+ ratio and efficient scavenging system by antioxidant agent (PVP) application or increase the endogenous antioxidant enzymes activities leading to minimize the negative effect of salt stress on in vitro grown potato.