Subsarcolemmal hyaline bodies were found in a skeletal muscle biopsy of a 10-year-old boy manifesting mild non-evolutive motor disturbances with frequent falls since early childhood. The hyaline bodies occurred in type I fibers and stained intensely with the myosin ATP-ase reaction at pH 4.2. They immunostained intensely with polyclonal anti-skeletal myosin and monoclonal anti-skeletal fast myosin. Additionally, immunoreactive deposits to anti-desmin were observed at the border of some bodies. At the ultrastructural level, these bodies were not surrounded by a limiting membrane and were only localized in subsarcolemmal areas. They contained moderately dense and disorganized filaments which appeared to be in continuity with thick myosin filaments of intact adjacent myofibrils. They stained negatively for polysaccharides according to the periodic acid-thiosemicarbazide silver proteinate method of Thiéry (1967). Analogies and differences with reported cases in the literature with similar subsarcolemmal deposits and other ultrastructural findings in congenital myopathies are discussed.