The aim of this research was to investigate the permeability of superfine cement-grouted sand. Initially, rheology of superfine cement suspensions was studied. The sedimentation and the setting time increased but the viscosity decreased as the water-cement ratio (w/c) increased. In addition, the penetrability of superfine cement suspensions with different w/c into various graded sand specimens prepared at different relative densities was tested. The penetrability of suspensions into the sand specimens was successful and increased as the w/c increased, but decreased as the relative density increased. Grouted sand samples were kept in a humidity room at a temperature of 20 degrees C (68 degrees F) until testing time and subjected to permeability tests at different time intervals. The coefficient of permeability increased as the w/c increased, but decreased as the relative density and the percentage of fines increased. Additionally, the coefficient of permeability of grouted samples decreased slightly with time.