The amplitude and time course of postsynaptic potentials (PSPs) recorded by intracellular techniques contain information that allow different synaptic events to be detected. In the present paper an algorithm to detect spontaneous PSPs is described. The algorithm is based on computation of approximations of first and second derivatives of the signals. The method was tested on both computer-simulated potentials and on experimental data recorded from dissociated mouse spinal cord neurons in tissue culture. The receiver operating characteristics of the detection algorithm were computed. This method can be applied to investigations of dynamic changes in the activity of neural networks.