Growth and some metabolic activities of two cyanobacterial species (Anabaena subcylindrica and Nostoc Linckia) grown under salinity stress with and without exogeneously added calcium chloride were monitored. Salinity treatment  (0.3M NaCl) induced pronounced reduction in growth, pigment fractions, carbohydrates, O₂–evolution, respiration, lipids content and increase in the measured elements content (Na⁺, K⁺, Mg⁺⁺, Fe⁺⁺⁺ and Ca⁺⁺). Presence of Ca²⁺ (0.03 or 0.05 M CaCl₂) caused significant recovery of the different measured growth parameters and metabolic activities.  The most important changes induced by salinity treatment are:1-Reduction in the polysaccharides content of both organisms accompanied with an increase in the soluble sugars, which proposed that the possible inhibitory effect of salinity associated with osmotic regulation. This effect could be ameliorated by addition of calcium ions. 2- The integrity of the plasma membranes impaired by salinity. Presence of calcium protects the membranes against the injury induced by salinity.