We present in this paper a new method,based on measurements of conventional direct current-voltage(I-V) characteristics and transient voltage-time(V-t) characteristics during the discharge process,for determining capacitance-voltage(C-V) characteris-tics of organic semiconductor devices.Derivatives of I-V and V-t,dI/dV and dV/dt,are related with C by a simple formula C=-V(dI/dV)/(dV/dt)The validity of the method is confirmed by experimental data measured from a set of single-organic-layer devices with different layer thicknesses. We present in this paper a new method, based on measurements of conventional direct current-voltage (IV) characteristics and transient voltage-time (Vt) characteristics during the discharge process, for determining capacitance-voltage (CV) characteris tics of organic semiconductor devices. Derivatives of IV and Vt, dI / dV and dV / dt, are related with C by a simple formula C = -V (dI / dV) / (dV / dt) from a set of single-organic-layer devices with different layer thicknesses.