Bulbocavernosus reflex was evaluated clinically in 299 patients during a routine urodynamic evaluation and compared to the electromyographic demonstration of the reflex. The findings were correlated with the neurologic status of the patients. There were 127 patients who were normal neurologically, and 98 per cent of the male and 81 per cent of the female patients in this group had a normal bulbocavernosus reflex clinically. All of the male and 92 per cent of the female patients had a bulbocavernosus reflex demonstrated by electromyography. There were 73 patients with neurologic lesions involving the sacral spinal cord. All patients with a complete lesion had absent bulbocavernosus reflexes clinically and on electromyography, while 44 per cent of the patients with incomplete sacral lesions had an intact bulbocavernosus reflex clinically and 78 per cent had reflex demonstrated by electromyography. There were 99 patients with neurologic lesions of the spinal cord above the sacral outflow, and 90 per cent of this group had demonstrable bulbocavernosus reflexes clinically and 93 per cent had the reflex demonstrated by electromyography. It is concluded that the absence of a bulbocavernosus reflex in a male patient is indicative of a neurologic lesion involving the sacral spinal cord and is highly suggestive of such a lesion in a female patient. The presence of a normal bulbocavernosus reflex in either sex does not rule out the possibility of a significant lesion. The electromyographic demonstration of the bulbocavernosus reflex is more sensitive than the clinical one.