We have established an improved method of sodium dodecyl sulfate-polyacrylamide gel electrophoresis to facilitate analysis of giant myofibrillar proteins connectin and nebulin, whose molecular masses are about 3000 and 700 kDa, respectively. This method consists of 2% polyacrylamide slab gels strengthened with agarose and a specific buffer system. Our 2% polyacrylamide slab gels are superior to usual 1.8 or 2% polyacrylamide disc gels in preparation, handling, and resolution.