A new simplified electrophoretic and Western blotting technique for the study of dystrophin in muscle biopsy material is presented and compared with immune histochemistry. The method is based on separation of dystrophin in a linear SDS-PAGE pore gradient of 4-8% acrylamide in ultra-thin, horizontal gels on plastic film support followed by horizontal electrotransfer for Western blotting. The advantages of this procedure are short separation and transfer times at high field strength, high resolution, short staining procedures and small requirements of chemicals. Samples from the same gel can be cut and examined with different antibodies. Final results are obtained in one day. Examination of patients with various types of muscular dystrophies verified the essential absence of dystrophin in DMD patients, and showed considerable dystrophin heterogeneity in patients with BMD. A girl with severe symptoms of dystrophy revealed unexpected dystrophin abnormalities. The results also indicated that SDS-PAGE with Western blotting and immune histochemistry are complementary, diagnostic, and research instruments, and that the reactivity of commercial antibodies may differ in these two techniques.