The pathogenesis of ALS is unknown, but there is convincing evidence that several molecular mechanisms play a role. Previous studies investigated the role of the Survival Motor Neuron (SMN) gene in ALS. Recent data suggest that SMN genotypes producing less SMN protein increase susceptibility and severity of ALS. This leads to the hypothesis that the clinical expression of ALS is influenced by the total SMN protein level in affected patients. In a population of ALS patients in the Netherlands we found that SMN genotypes producing less SMN protein appear to increase susceptibility and severity of ALS. It was shown that the HDAC inhibitor sodium valproate (SVP) increases levels of SMN protein in vitro. From these results and from data suggesting neuroprotective properties of SVP, it is hypothesised that SVP could extend survival of patients with ALS. In addition, sodium valproate significantly prolonged the disease duration in the animal model for ALS, the SOD1 transgenic mouse. Given that SVP is a FDA-approved compound with well-known pharmacokinetic and toxicity profiles, it is an attractive candidate for a clinical trial in ALS patients.