Motor neuron diseases such as amyotrophic lateral sclerosis (ALS) and spinal muscular atrophy (SMA) are characterized by the progressive loss of motor neurons in the spinal cord and primary motor cortex. Subsequent paralysis of skeletal muscles leads to variable degrees of motor impairment and is inevitably fatal in ALS and type I SMA. A genetic cause has been defined for some of these conditions including SMA. Therefore, motor neuron disorders could become prime targets for gene therapy provided efficient tools can be designed to specifically target widely distributed motor neurons. Here, the application of viral vectors with a neuronal tropism is reviewed in the context of gene delivery to spinal lower motor neurons. The preparation of adeno-associated vector suspensions for motor neuron infection is described. Finally, we emphasize the use of intramuscular and intracerebroventricular delivery of adeno-associated vectors for the specific targeting of motor neurons.