The transfer function of a turbid medium such as biological tissue provides a method of analyzing the spatial resolution of a time-resolved tissue imaging system. A method is presented of calculating the transfer function with the use of a Monte Carlo simulation. The model allows the computation of the time-resolved line-spread function of a sample of thickness $d/2$ from a simulation of thickness $d/2$ by use of reciprocity under certain conditions, and the transfer function can then be computed from the line-spread function. Results with this method agree with previously published theoretical and experimental results.