Induction of thermotolerance by calcium and heat acclimation was studied in two wheat cultivars namely PBW 343 (heat tolerant) and WH 542 (heat susceptible) under heat stress conditions. One day old wheat seedlings germinated at 25oC were treated with Ca2+ (10 mM) prior to heat acclimation (35oC) and heat shock (45oC) treatments for 2 h and thereafter maintained a 25oC for 5 days in dark. Seedlings at 25oC without calcium, heat acclimation and heat shock treatments were kept as control. Heat shock treatment resulted in decrease in antioxidative enzymes viz. peroxidase (E.C.220.127.116.11), superoxide dismutase (E.C.18.104.22.168) and catalase (E.C.22.214.171.124) in both cvs. Similarly, respiratory activity measured as triphenyl tetrazolium chloride as cell viability and chlorophyll content also declined whereas electrolyte leakage increased during heat shock indicating damage to cell membranes. However, Ca2+ pretreatment along with heat acclimation led to greater increase in activities of antioxidative enzymes, cell respiration in PBW 343 as compared to WH 542, indicating, thereby induction of thermotolerance which is further reflected in differential heat sensitivity of two cultivars studied.