Motor neuron death as seen in amyotrophic lateral sclerosis (ALS) is likely to be a non-cell autonomous process. One cell type that may be involved in the pathogenesis of the disease is the astrocyte. Under normal conditions, astrocytes affect survival of motor neurons by releasing growth factors and removing glutamate from the synaptic cleft. In addition, they determine some of the functional characteristics of motor neurons. In turn, motor neurons affect the functional characteristics of astrocytes. Recent evidence suggests that activation of astrocytes in a degenerative disease like ALS leads to a disturbance of this crosstalk between astrocytes and motor neurons, and that this may contribute to the death of motor neurons. As a consequence, understanding the interactions between motor neurons and astrocytes in health and disease may have important therapeutic implications.