In chemonucleolysis, accuracy of injection can be in doubt if the patient fails to respond. Discography preceding chemonucleolysis is associated with increased neurologic complications. Biplane fluoroscopy may fail to provide a clear picture on many occasions. The serum keratan sulphate levels were estimated in patients undergoing chemonucleolysis to ascertain if this could be used as a biochemical indicator to confirm accurate needle placement and to predict outcome. Serum keratan sulphate levels rose significantly following chemonucleolysis during the first 3 days (P<0.01). The rise was not significantly different, however, in patients who had improvement in their leg pain from those who did not improve (P= 0.35). Serum keratan sulphate level estimation before chemonucleolysis and at 24 or 48 hours following the procedure can be used to confirm accuracy of needle placement, but the rise in keratan sulphate is not predictive of the clinical outcome of the procedure.