The effects of melt temperature and mold preheating temperature on the fluidity of Ca containing AZ31 alloys were evaluated under various casting conditions. The flow lengths of AZ31-xCa alloy melt increased with increasing the melt temperature due to lower viscosity and longer time to fill the mold cavity. The increment of the flow lengths of AZ31-xCa alloy melt with increasing the mold preheating temperature was not large due to large diameter of circular cross section of mold cavity. The fluidity of AZ31-xCa alloy melts was affected more forcefully by melt temperature than by mold preheating temperature under casting conditions used in this study. Also, the flow lengths of AZ31-xCa alloy melt were affected by grain size of primary solid particles solidified during filling mold cavity and surface oxide film due to addition of Ca. (c) 2006 Springer Science + Business Media, Inc.