Flotation deinking experiments were conducted in order to understand the effects of surfactant, pH, and electrolyte concentration on old news paper deinking efficiency. Both removal efficiency and brightness were found to increase in anionic surfactant systems both at acid and alkali conditions, because added counter ions reduced electrostatic repulsion between negatively charged air bubbles and ink particles. IN mixed surfactant systems, both removal efficiency and brightness were shown to increase with a decrease in pH, mainly due to reduction in electrostatic repulsion by an increase of hydrogen ion concentration. When electrolytes were added un anionic surfactant systems or mixed surfactant systems, ink removal efficiency increased or decreased, depending on the change in electrostatic repulsion between ink particles and air bubbles. On the other hand, both pH change and addition of electrolytes did not have a significant effect on physical strength of the pulp fiber, and contact angle and surface tension of the ink particle.