Simultaneous ground based radar reflectivity measurements and airborne electric parameters (electrostatic field and charged particles) are presented. They are used to investigate the charging processes acting in convective cells. Within the two thunderclouds presented in this work, both signs are found on large hydrometeors. It is shown that negative particle charging exists at high levels in classical vertically developed cells. There is some evidence that positive charging of precipitating particles is occurring in the lower parts of the clouds.