A series of balloon soundings was conducted in which the biopolar ion density, conductivity and ion production rate profiles were measured. Near-simultaneous measurements of the aerosol profile were also made. The results are used to calculate profiles of the effective average mobility and the recombination coefficient. Above the atmospheric boundary layer, both polarities of ions were found to have relatively constant mobilities to balloon ceiling (35 km) with the positive ion mobilities being somewhat smaller at low altitudes and somewhat larger at high altitudes. The absolute value of the mobilities was somewhat smaller than those calculated from measurements of the ion mass. It was also found that the value of the recombination coefficient calculated from the basic flight data agrees well with theory. The basic ion equilibrium equation was tested by making soundings at two locations where the cosmic ray ion production rate differed significantly in the stratosphere. The results indicate that the equation is, in fact, generally applicable to the stratosphere. A considerable effort was made to obtain mobility profiles during atmosphere events when it was believed that there was a high probability of heavy H2SO4 ions being present. However, only minimal evidence was found for existence of these ions. ¿ American Geophysical Union 1988