Exon skipping of dystrophin in mdx mice has been the key model for the development of antisense therapy in vivo. Evaluation of exon skipping in this model involves the following two aspects: (1) efficiency and accuracy of exon skipping and levels of dystrophin expression determined by RT-PCR, immunochemistry and western blotting; (2) therapeutic effects on muscle pathology and functions assessed by histology and functional assays including grip strength measurement, treadmill exhaustion test, plethysmography for respiratory functional analysis and echocardiogram and hemodynamics for cardiac functions. Here we describe some key consideration and the essential methodologies in detail for exon skipping in mdx mice.