Up to now, baclofen (a GABA(B) receptor agonist) has been used for the treatment of severe spasticity unresponsive to oral antispasmodics. Although in humans it is usually administered at 2 mg/ml, the dosage to be used in the treatment of other diseases is unknown. For this reason, it is important to determine the safe maximum dosage and toxicity at the clinically used concentration. Primary cortical neurons represent a useful model to test the safety of baclofen. We performed a colorimetric assay (MTT test) as well as electron microscopy investigations, to determine neuronal survival after the treatment with baclofen at a concentration of 2 and 4 mg/ml. Our results demonstrated that, in our experimental model, neither concentration affected neuronal survival. Considering the above results, we can conclude that at the used concentrations, this drug is safe and its clinical use should be encouraged.