The solubility of manganese in YFe1-yMnyO3 reaches y = 0.4. Among these compositions, YFe0.6Mn0.4O3 has the highest conductivity with a = 2.16 Omega (-1). cm(-1) (1000 degreesC, air), which is >1 order of magnitude higher than that of yttrium ferrite, YFeO3 (sigma = 0.10 Omega (-1). cm(-1), 1000 degreesC, air). In the range 0.2 less than or equal to y less than or equal to 0.4, the conductivity is linearly proportional to the manganese content. The mechanism of direct transport of polarons among manganese sites (y greater than or equal to 0.2) is proposed to explain the electrical behavior of manganese-doped samples, X-ray diffractometry and infrared spectroscopy have been applied for the structural characterization of the samples.