The splitting of the connectin (titin) molecule during meat conditioning and its primary structure were analyzed. Using immunofluorescence microscopy and immunoelectron microscopy, it was showed that the connectin molecule split into β-connectin and 1,200 kDa-subfragment at a point 0.34 μm apart from the Z-disc during meat conditioning. Differences in molecular weight and partial amino acid sequences of connectin were determined for cattle, pig and chicken skeletal muscles. Results of peptide mapping analysis differed according to animal species. Amino acid sequences deduced from partial nucleotide sequences of connectin also differed according to animal species at immunoglobulin-like (Ig) and fibronectin type 3(FN3) domains. In chicken, the molecular weight of connectin from leg muscles differed from the value recorded in pectoral muscles. It is suggested that meat texture and conditioning may be related to the splitting of the connectin molecule and its structure.