An effective method for gene delivery into spinal motor neurons is required for gene therapy for the motor neuron diseases such as amyotrophic lateral sclerosis or spinal muscular atrophy. Recombinant adeno-associated virus (rAAV) vectors serve as powerful tools for gene therapy of neurological diseases due to efficient transduction of genes in neurons and apparent lack of pathogenicity in humans. The present study compared rAAV vector serotypes 1, 2, 5, 6, and DJ for transduction efficiency to motor neurons in rats following intramuscular injection. Each of these rAAV 1-DJ serotype vectors with an enhanced green-fluorescent protein (EGFP) reporter gene was injected into the triceps brachii muscle of rats at postnatal days 8 and 21. Four weeks after the injection, rAAV 1 resulted in the highest level of retrograde EGFP expression in the ipsilateral motor neurons in both groups of rats. The result indicated that rAAV 1 is suitable for retrograde transduction of gene expression in motor neurons. A number of afferent neurons in the ipsilateral DRG also expressed EGFP. Currently, we developed rAAV vectors carrying enhancer elements of Hb9 promoter for selective expression of the transgene in motor neurons.