An analysis of the north-south asymmetry in the cosmic ray flux was made with data taken in the north and south polar atmosphere from 1963 through 1991. For altitudes corresponding to column densities between 100 and 800 g/cm2 the N-S asymmetry is near zero during the negative phase of the solar magnetic cycle (1963--1969 and 1982--1989) and is positive during the positive one (1972--1979). The maximum amplitude of N-S asymmetry (up to 3%) occurs at an atmospheric depth of X=500--600 g/cm2 and could be caused by primaries with rigidities of more than 30--50 GV. At higher altitudes, X<25 g/cm2 during almost all periods an excess of particles in the northern polar hemisphere was observed. This excess is due to the presence of reentrant albedo electrons on closed magnetic field lines. ¿ American Geophysical Union 1996