A new technique is proposed for switch-level logic simulation for NMOS and CMOS logic circuits. For the simple inverter the rise or fall delay time is approximated by a product of polynomials of the input waveform slope, the output loading capacitance and the device configuration ratio, the polynomial coefficients being so determined as to best fit the SPICE simulation results for a given fabrication process. This approach can easily and accurately be extended to the case of multiple input transitions. The simulation results show that the proposed method can predict the delay times within 5\% error and with a speed up by a factor of three orders of magnitude for several circuits tested, as compared with the SPICE simulation.