Abstract: The invention relates to adeno-associated virus (AAV) vectors encoding superoxide dismutase (SOD), where the AAV vector encoding SOD (AAV-SOD) may be used to deliver the SOD gene to target cells. The target cells may be within a subject having a disease or condition for which delivery of SOD to the target cells provides a therapeutic benefit and/or a therapeutic effect on the subject. In another aspect, the invention relates to a model system for screening compounds for efficacy in treatment of amyotrophic lateral sclerosis (ALS). The model system may comprise a plurality of cells transduced with an AAV vector encoding an SOD gene; the transduced cells may exhibit a phenotypic change associated with ALS.