This is the first report of multielectrode recordings from networks of cultured motor neurons. Neurons isolated from the ventral horns of spinal cords of E15 rats were cultured on MED64 probes. The majority of the neurons in the cultures are positive for neurofilament, choline acetyltransferase, and Hb9, characteristics of motor neurons. The activity of the motor neuron network is characterized by spiking of individual cells as well as spontaneous, synchronized bursts involving all active electrodes. Both spiking and network bursts are stimulated by GABA antagonists and acetylcholine, and are inhibited by GABA itself and glutamate antagonists. Networks of cultured embryonic motor neurons make a good model system for studying motor neuron development and physiology as well as the pathophysiology of motor neuron disease.