The toner charge-to-mass ratio (Q/M) and toner mass per unit area (M/A) on both the developing roll and organic photoconductor (OPC) drum in a nonmagnetic mono component contact development system were studied by adjusting the dc bias. The bias between the developing roll and toner-adding roll from −200 to 200 V (V_dr−V_tar), and the bias between the developing roll and doctor blade from −400 to 600 V (V_dr−V_b) were the ranges of interest. The development potential between the developing roll and the OPC drum was kept at a constant value of 220 V. The developing roll, 2.0 cm in diameter, is made of soft polyurethane with a bulk electrical resistivity of 10¹⁰Ω-cm. The OPC drum used here has a diameter of 3.0 cm. The average Q/M ratio of toner on the developing roll is larger than that on the OPC drum corresponding to each V_dr−V_b when V_dr−V_tar is changing from 0 to 200 V. The Q/M ratios are affected by V_dr−V_b more on the OPC drum than on the developing roll. M/A ratios on both the developing roll and the OPC drum increased linearly as V_dr−V_tar was increased from −100 to 50 V and were nearly constant (changing within 0.2 mg/cm²) under a constant V_dr−V_b of 200, 400, and 600 V as V_dr−V_tar increased from 100 to 200 V.