To understand spatiotemporally coordinated activity in neural networks and interaction between different areas or layers in brain tissue, simultaneous multisite recording is a prerequisite. For in vitro studies pursuing these goals, substrate integrated, planar microelectrode arrays (MEAs) have been developed to monitor spikes and local field potentials. Here we report for the first time recordings of single-unit spike activity with MEAs in acute slice preparations of the rat cerebellum. We compare these recordings to results of conventional techniques, and discuss the recording conditions in view of the equivalent circuits commonly used. Simultaneous recordings with tungsten microelectrodes and MEAs verified that recording characteristics and signal-to-noise ratios of MEA electrodes were comparable to those of conventional extracellular electrodes. Spike shapes were identical on both electrodes. We found no detectable overlap between spike signals recorded at neighboring MEA electrodes (200 microm spacing). Neuronal spike activity was detected with MEA electrodes at distances of up to 100 microm from the site of spike generation. We conclude that extracellular recording of independent single-unit spike activity with MEAs is indeed suitable to monitor network activity in acute slices, making MEAs an exceptionally useful tool for the assessment of fast network dynamics in acute slices.