Catharanthus roseus (L.) G. Don. plants were grown with NaCl and CaCl₂ in order to study the effect of CaCl₂ on NaCl-induced oxidative stress in terms of lipid peroxidation (TBARS content), H₂O₂ content, osmolyte concentration, proline (PRO)-metabolizing enzymes, antioxidant enzyme activities, and indole alkaloid accumulation. The plants were treated with solutions of 80 mM NaCl, 80 mM NaCl with 5 mM CaCl₂ and 5 mM CaCl₂ alone. Groundwater was used for irrigation of control plants. Plants were uprooted randomly on 90 days after sowing (DAS). NaCl-stressed plants showed increased TBARS, H₂O₂, glycine betaine (GB) and PRO contents, decreased proline oxidase (PROX) activity, and increased γ-glutamyl kinase (γ-GK) activity when compared to control. Addition of CaCl₂ to NaCl-stressed plants lowered the PRO concentration by increasing the level of PROX and decreasing the γ-GK activities. Calcium ions increased the GB contents. CaCl₂ appears to confer greater osmoprotection by the additive role with NaCl in GB accumulation. The antioxidant enzymes superoxide dismutase (SOD), peroxidase (POX) and catalase (CAT) were increased under salinity and further enhanced due to CaCl₂ treatment. The NaCl-with-CaCl₂-treated C. roseus plants showed an increase in total indole alkaloid content in shoots and roots when compared to NaCl-treated and untreated plants. To cite this article: C. Abdul Jaleel et al., C. R. Biologies 330 (2007).