Lumbar myelographic defects consistent with herniated disc were found in 108 asymptomatic patients undergoing myelography for other reasons. Within 3 years, 64% of these patients developed symptoms of lumbosacral radiculopathy. The clinical features of these patients comprise a syndrome significantly different from that typically associated with classical lumbar disc herniation: the syndrome described here carries a much higher incidence of silent root compression with minimal pain. Incidental lumbar myelographic defects are not necessarily benign findings, and patients in whom they are encountered deserve close clinical follow-up review and appropriate treatment if the defects become symptomatic.