A 4-year-old boy suffering from a nonprogressive muscular weakness had a muscle biopsy which ultrastructurally showed large aggregates of nemaline bodies and mitochondria in myofibers; occasional concentric lamellated bodies were present as well. The mitochondria were mostly at the periphery of collections of nemaline bodies, less commonly in their central portions. The light microscopic features differed from those of either nemaline or mitochondrial myopathy and were somewhat reminiscent of multicore disease. Evidence suggestive of possible neurogenic origin of both rods and mitochondria is reviewed.