Systematic discrepancies have been observed between ion density measurements taken by the electrostatic analyzers on ISEE 3 and the Faraday cup and electrostatic analyzer on board the IMP 8 spacecraft during the International Magnetospheric Study. We have quantified these discrepancies as a function of solar wind bulk velocity and ion temperature, and have developed correction algorithms that should bring all density measurements to a common base. The electron densities from ISEE 3 are used as the intercalibrating base, since these measurements of the solar wind density should not depend on the ion velocity or temperature. ¿ American Geophysical Union 1993