We investigated the spread of spinal anesthesia with hyperbaric dibucaine in 20 adolescents aged 9-18 yr and 20 adults aged 23-53 yr. No significant difference was found between the two groups with regard to height, whereas a statistical significant was found between the two groups with regard to weight. Spinal anesthesia was conducted with Neo-Percamin S injected at the L3-L4 interspace through a 25-gauge spinal needle. Injected volumes of the anesthetic solution were calculated from the patients' height at 0.01 ml.cm(-1). In adolescents, 1.6 +/- 0.1 ml (mean +/- SD) of the anesthetic solution produced 19.4 +/- 1.5 spinal segments blocked. In adults, 1.6 +/- 0.1 ml of the solution produced 13.4 +/- 1.6 spinal segments blocked. A high spinal anesthesia above T5 was achieved in 17 (85%) patients in adolescents, whereas such a high level of spinal anesthesia was not experienced in adults. These results suggest that the hyperbaric dibucaine solution for spinal anesthesia in adolescents may have a tendency to produce an unexpectedly extensive spread of anesthesia.