Verbiest (1973) reported lumbar stenosis in 2 brothers, aged 43 and 47 years. One had relative stenosis at L4 and absolute stenosis at L5; the other had relative stenosis at L4. Verbiest (1976) also reported 2 affected sisters. ... Verbiest (1973) reported lumbar stenosis in 2 brothers, aged 43 and 47 years. One had relative stenosis at L4 and absolute stenosis at L5; the other had relative stenosis at L4. Verbiest (1976) also reported 2 affected sisters. Varughese and Quartey (1979) described the cases of 4 brothers with acute lumbar disc herniation and myelographic narrowing of the lumbar spinal canal in the sagittal plane. Postacchini et al. (1985) reported the cases of 2 brothers and a sister 'with developmental or combined lumbar stenosis.' The father of the sibs and the son of 1 of them may be affected also. Computerized tomographic views of the lumbar spine were presented, showing constitutional narrowing of the lumbar spinal canal. Dejerine (1914) described 'intermittent claudication of the spinal cord.' In advanced spinal stenosis the patient walks in an acutely 'bent-over' posture. Spinal stenosis is very frequent in achondroplasia (100800), which is another form of constitutionally small lumbar spinal canal. In the bent-over position, the sitting position, and the bicycling position, the capacity of the lumbar spinal canal is maximized. Patients with achondroplasia who have serious limitation of walking can usually bicycle without limitation. Hopkins et al. (1987) described penile erections on walking as a symptom of spinal canal stenosis. Loss of erectile potency is a more frequent manifestation.