The work presents the results of low-temperature (220-300 K) studies of electrical conductivity and thermoelectric power for manganese spinel obtained by various methods. It has been shown that charge transport takes place through the small polaron mechanism. The results of high-temperature (300-1100 K) studies of electrical conductivity and thermoelectric power carried out in the thermodynamic equilibrium conditions as a function of temperature and oxygen pressure (10(-2) - 1 atm) in the whole range of the LiMn2O4-delta phase stability are also presented. It has been shown that an effective reaction related to the deviation from stoichiometry is the reaction Mn+4 + e(-)double left right arrow Mn+3.