Subsolidus phase relations have been determined in the CdO-InO1.5SnO2 system at 1175degreesC. A cubic-bixbyite solution ln(2-2x)(Cd,Sn)(2x)O-3 to < x < 0.34), a cubic spinel solution (1-x)CdIn2O4-xCd2SnO4 (0 < x < 0.75), and an orthorhombic-perovskite solution Cd1-xSn1-xIn2xO3 (0 < x < 0.045) having the GdFeO3 structure have been discovered. The CdO phase field exists over a small range of InO1.5 (<3%) and SnO2 (<1%). Orthorhombic Cd2SnO4 (Sr2PbO4 structure) and rutile SnO2 appear to be point compounds with negligible solubility. The vertical section between spinet CdIn2O4 and orthorhombic Cd2SnO4 was determined between 900degrees and 1175degreesC. The spinel phase field (1-x)CdIn2O4-xCd(2)SnO(4) was found to extend between x = 0 and x = 0.75 at 1175degreesC or x = 0.78 at 900degreesC. All of the phases in this system appear to allow small excess quantities of the donors In and/or Sn (vs cation stoichiometry) which may be the source of the electrons that give these oxides their n-type character. The electrical and optical properties of bulk and thin-film specimens in this system are compared and contrasted with each other and the relative merits of each are assessed.