 Spinal muscular atrophy SMA is an autosomal recessive disorder that affects the motoneurons of the spinal anterior corn, resulting in hypotonia and muscle weakness. The knowledge about its molecular mechanism has led to clinical tests with drugs that increase survival motor neuron SMN protein level. The valproic acid VA that acts as a histone deacetylase inhibitor activates the SMN2 gene increasing the protein level. Methods: Twenty-two patients with type II and III SMA, aged between 2 and 18 years old, were treated with VA and were evaluated five times along a period of one year using the Manual Muscle Test Medical Research Council scale-MRC, the Hammersmith Motor Ability Score, and the Barthel Index. The first evaluation was coincident with the introduction of VA. Results: After 12 months of therapy, the patients did not gain muscle strength but their motor ability has improved. Children younger than 6 years of age had a higher pronounced gain in motor ability. Conclusion: treatment of SMA patients with VA is one alternative to alleviate the progression of the disease. 