Sarcoplasmic or endoplasmic reticulum Ca2+ ATPase (SERCA2) was localized in the ameloblasts of rat incisors by immunohistochemistry. Secretion ameloblasts and maturation ameloblasts, including both ruffle-ended and smooth-ended cells, were labeled with anti-SERCA2 antibodies, with maturation ameloblasts showing stronger binding than secretion ameloblasts. The pattern of labeling was cytoplasmic and diffuse. Papillary layer cells were not labeled with anti-SERCA2 antibodies. These results suggest that the SERCA2 in ameloblasts is intimately involved in mineralization during amelogenesis.