Changes in shear force value, transverse sections, myofibrils and intramuscular connective tissue of bovine skeletal muscle exposed to the combination of high-pressure up to 400 MPa and heat (30 and 60 degrees C) were studied. The shear force value decreased by pressure-heat treatment up to 200 MPa at 30 and 60 degrees C, and then slightly increased over 200 MPa at 30 degrees C. Shear force values of treated muscles were lower than those of untreated ones. Gaps between muscle fibers in the untreated muscle were a little clear, and then they became very clear in the treated muscles up to 200 MPa at 30 and 60 degrees C. However, the gaps reduced significantly over 200 MPa at 30 degrees C. The remarkable rupture of 1-band and loss of M-line materials progressed in the myofibrils with increasing pressure applied. However, degradation and loss of the Z-line in myofibrils observed in the muscle treated at 60 degrees C was not apparent in the muscle treated at 30 degrees C. The length of the sarcomere initially contracted by pressure-heat treatment of 100 MPa at 30 degrees C seemed to have recovered with increase of the pressure up to 400 MPa. In the muscle treated at 60 degrees C, the length of sarcomere gradually decreased with increase of the pressure up to 400 MPa. In the treated muscles, changes in the honeycomb-like structure of endomysium were observed and accelerated with increase of the pressure. A wavy appearance clearly observed at the inside surface of endomysium in the untreated muscles gradually decreased in the treated muscles with increase of the pressure. Tearing of the membrane was observed in the muscles treated over 150 MPa at 30 degrees C, as observed in the sample pressurized at 100 MPa at 60 degrees C. The roughening, disruption and fraying of the membrane were observed over 200 MPa at 60 degrees C. From the results obtained, the combination of high-pressure and heat treatments seems to be effective to tenderize tough meat. The shear force value may have some relationship with deformation of intramuscular connective tissue and myofibrils.