Experimental studies on drag reduction of a circular cylinder of diameter D were conducted in the subcritical flow regime at Reynolds numbers in the range $4{ imes}10^4{leq}Re{leq}10^5$. To shield the cylinder rear surface from the pressure deficit of the unsteady vortex generation in the near wake, two shield plates were attached downstream of the separation points to form a cavity at the base region. The chord of the shield plates, L, ranged from 0.22 to 1.52 D and the cavity width, G, was in the range from 0 to 0.96 D. It is concluded that significant drag reductions from that of a plain cylinder may be achieved by proper sizing of the shield plates and the base cavity. The study shows that using a pair of shield plates at G/D of 0.86 and angular position ${ heta}$ of ${pm}121^{circ}$ results in a configuration with percentage drag reduction of 40% for L/D of 0.5, and 55% for L/D of 1.0.