Three and five millilitre of india ink were injected bilaterally into the costal groove of the 9th or 10th ribs of 14 cadavers. The spread was observed and the costal groove of the rib injected was dissected, with the one above and one below. Nunn and Slavin's study (1980) of similar injections in two cadavers indicated that an injection of one costal groove blocked not only the intercostal nerve of that groove, but at least the one above and below it. The present study verified the author's previous report that only the intercostal nerve in the costal groove of the rib injected is anaesthetized.