Effective Interactions between Macroions 1.- Dilute Solutions of Flexible and Spherical Ionic Polymers.- Colloidal Dispersions.- Kikuchi-Kossel Line Analysis on Colloidal Crystals.- Effective Interactions between Macroions 2.- Viscometric Properties of Dilute Ionic Polymer Solutions and Colloidal Dispersions.- Phase Transitions by Computer Simulation.- Further Problems of Interparticle Interaction.