It has been suggested that the extensive longitudinal extradural spread of local anaesthetics in the elderly is attributed to decreased leakage through the intervertebral foramina. We have examined radiologically, in 53 patients, the relationship between leakage of iohexol through the thoracic intervertebral foramina and age. Iohexol was injected through an extradural catheter advanced 5 cm cephalad from one of the interspaces between T6 and T12. A significant correlation was observed between longitudinal spread of iohexol and age, but there was no correlation between leakage of iohexol through the intervertebral foramina and age. Our data suggest that longitudinal extradural spread of local anaesthetics in the elderly may not be attributed to decreased leakage through the intervertebral foramina.