A girl developed progressive weakness of bulbar and ocular muscles starting before the age of two years. Electromyography revealed a widespread subclinical myopathy. An intercostal muscle biopsy showed complex abnormalities including occasional neurofilamentous accumulations and honeycomb-like membranous material in terminal axons. Endplates were small and some secondary synaptic clefts were abnormally deep. Acetylcholine receptors extended unusually deeply into the clefts of the junctional folds. Muscle fibres showed subsarcolemmal vacuolation at some places. This form of congenital oculo-bulbar palsy does not appear to have been described previously.