Several authors have previously reported the complications resulting from contact between a diagnostic or therapeutic agent injected into an intervertebral disc and neural tissue. This study was undertaken to demonstrate the common routes by which, and frequency with which this contact occurs. Of 105 cadaveric intervertebral discs studies, 15 (14%) leaked. Of the discs that leaked, 27% demonstrated contact of injected dye with the adjacent spinal nerve. The high rate of leakage may be related to the age of the cadavers. Nonetheless, the contact between substances injected into an intervertebral disc and adjacent neural tissue during discography offers an alternate mechanism of pain reproduction in an incompetent disc. It also suggests that nontoxic agents should be used for discography and that intervertebral discs should be proved competent before chemonucleolysis]