The ferromagnetic compoundLa3−3xCa1+3xMn3O10with a triple perovskite structure can be successfully synthesized by using a thin-film growth method. Sputtereda-axis thin films withx=0.3have been examined with respect to their magnetotransport properties. For the triple perovskite compound, we have observed the features, including the enhanced magnetoresistene (MR) effect and the characteristic low-temperature MR effect resulting from intragrain spin-polarized tunneling, which were reported for the double perovskite manganites. A comparison of the magnitude of these features in triple and double perovskite manganites suggests that the features are actually determined by thec-axis Mn–O bond configuration in a layered-perovskite ferromagnet. ©1997 American Institute of Physics.