Slices of CNS tissue prepared from young rodents can be maintained in culture for many weeks to months. The basic requirements are simple: a stable substratum, culture medium, sufficient oxygenation and incubation at a temperature of about 36 degrees C. Under these conditions, nerve cells continue to differentiate and to develop a tissue organization that closely resembles that observed in situ. Several alternative culturing methods have been developed recently. Slices maintained in stationary culture with the interface method are ideally suited for questions requiring a three-dimensional structure, whereas slices cultured in roller-tubes remain the method of choice for experiments that require optimal optical conditions. In this report, three typical experiments are discussed that illustrate the potential of the slice-culture technique. The first example indicates that, due to their high neuronal connectivity, slice cultures provide a very useful tool for studying the properties of synaptic transmission between monosynaptically coupled cell pairs. The other two studies show how long-term application of substances to slice cultures can be used to examine the consequences of epileptic discharges in vitro, as well as the effects of slowly acting clostridial neurotoxins on synaptic transmission.