Creep rupture tests were performed for die-cast AM50 + xCa (x = 0.47, 0.95 and 1.72 mass pct) alloys at temperatures between 423 and 498 K. The creep curve for the alloys is characterized by a minimum in the creep rate, and the decrease in creep rate during transient stage becomes pronounced with calcium concentration. The minimum creep rate (epsilon over dot(m)) and the creep rupture life (t(rup)) follow the phenomenological Monkman-Grant relationship for each alloy; t(rup) = Co/epsilon over dot(m)(m). It is found that the exponent m is unity for the alloys and the constant Co is independent of creep testing temperature, which is reduced with increasing calcium concentration. (C) 2008 Elsevier B.V. All rights reserved.