The present invention relates to a modified pig as a model for studying Alzheimer's disease. The modified pig model displays one or more phenotypes associated with Alzheimer's disease. Disclosed is also a modified pig comprising a modified human and/or porcine APP gene, and/or PS1 gene, and/or a transcriptional and/or translational product or part thereof. The invention further relates to methods for producing the modified pig; and methods for evaluating the effect of a therapeutical treatment of Alzheimer's disease; methods for screening the efficacy of a pharmaceutical composition; and a method for treatment of a human being suffering from Alzheimer's disease are disclosed.