The partial dislocations bordering a stacking fault and appearing on a coherent twin boundary in a Ni-Cr alloy (20% Cr, 1% Al, 2.5% Ti) were studied by TEM and the findings are as follows:1. The using of g·bp=±2/3 or ±1/3 as the criterion of appearance or disappearance of partial dislocations is acceptable, though not rigorous. Therefore, it is preferrable to choose {220} or {311} reflections to form diffraction contrast image and use g·bp = 0 to determine the Burgers vectors of the partial dislocations.2. Partial dislocation pairs appeared on coherent twin boundaries as a consequence of the dissociation of perfect dislocations.3. Stacking faults on parallel slip planes move and sometimes overlap each other. In overlapping faults the partial dislocations separating intrinsic and extrinsic faults showed no contrast when g·bp = ± 2/3 and appeared as white lines on the dark background of stacking faults, while they appeared as dark lines when g·bp= ± 1/3.