Results of spike-sorting algorithms are usually compared with recorded signals which themselves underly interpretations, distortions and errors. Our approach is to provide and compare physiological extracellular potential data by a realistic cortical network simulation. For this purpose, we utilize the neural simulator GENESIS and simulate a region of rat hippocampus containing 90 cells. We are able to "record" simulated extracellular potentials from "virtual electrodes" and produce test data closely resembling multisite neuronal recordings. Our realistic, artificial data are complex and almost natural in appearance; however, current spike detection schemes appear unable to reliably detect all spikes produced.