Single phase (Ca1-xNax)MnO3-delta with 0 <= x <= 0.025 is successfully fabricated using a solid state reaction in air. Electrical resistivity measurements indicate that oxygen vacancies are introduced into the (Ca1-xNax)MnO3-delta at high Na concentration (0.02 <= x). The hole carriers may be doped in (Ca0.99Na0.01)MnO3-alpha which has the lowest resistivity and smallest band gap. The highest signal for the imaginary part of magnetic susceptibility is shown by (Ca0.99Na0.01)MnO3-alpha at about 115 K. This high signal may be due to magnetic interactions between Mn4+ and Mn6+. (c) 2007 Elsevier B.V. All rights reserved.