We have grown almost dislocation-free ZnO crystals by the hydrothermal method. The variation of electrical properties on growth sectors of these crystals was studied by means of I-V and 1/C-2-V measurement. Gold contacts were made at the polar faces on each growth sector. In the (0 0 0 (1) over bar) faces [O surface] of all the sectors, clear rectifying action was observed. In the (0 0 0 1) faces [Zn surface] of all sectors, weak rectifying action or nearly ohmic characteristics were observed. These results indicate that the O surfaces tend to induce intrinsic defects like O vacancies and the rectifying characteristics become strong, while Zn surfaces tend to form a metallic face so that the Au contacts become ohmic. The variation of I-V and 1/C-2-V characteristics on the growth sectors showed that the contacts of m growth sector have better characteristics than those of other sectors.